User data compression method and apparatus for preventing data loss in wireless communication system

ABSTRACT

A communication method and system for converging a 5 th -Generation (5G) communication system for supporting higher data rates beyond a 4 th -Generation (4G) system with a technology for Internet of Things (IoT) is provided. The disclosure may be applied to intelligent services based on the 5G communication technology and the IoT-related technology, such as smart home, smart building, smart city, smart car, connected car, health care, digital education, smart retail, security and safety services. The disclosure provides a method and an apparatus for preventing data loss.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation application of prior application Ser.No. 16/870,179, filed on May 8, 2020, which is based on and claimspriority under 35 U.S.C. § 119(a) of a Korean patent application number10-2019-0053577, filed on May 8, 2019, in the Korean IntellectualProperty Office, the disclosure of which is incorporated by referenceherein in its entirety.

BACKGROUND 1. Field

The disclosure relates to a method and an apparatus for preventing dataloss when an uplink user data compression process is performed in awireless communication system.

2. Description of Related Art

To meet the increasing demand for wireless data traffic since deploymentof 4th generation (4G) communication systems, efforts have been made todevelop an improved 5th generation (5G) or pre-5G communication system.Therefore, the 5G or pre-5G communication system is also called a‘Beyond 4G Network’ or a ‘Post LTE System’. The 5G communication systemis intended to be implemented in higher frequency (mmWave) bands, e.g.,60 GHz bands, so as to accomplish higher data rates. To decreasepropagation loss of the radio waves and increase the transmissiondistance, the beamforming, massive multiple-input multiple-output(MIMO), Full Dimensional MIMO (FD-MIMO), array antennas, an analog beamforming, large scale antenna techniques are discussed in 5Gcommunication systems. In addition, in 5G communication systems,development for system network improvement is under way based onadvanced small cells, cloud Radio Access Networks (RANs), ultra-densenetworks, device-to-device (D2D) communication, wireless backhaul,moving network, cooperative communication, Coordinated Multi-Points(CoMP), reception-end interference cancellation and the like. In the 5Gsystem, Hybrid FSK and QAM Modulation (FQAM) and sliding windowsuperposition coding (SWSC) as an advanced coding modulation (ACM), andfilter bank multi carrier (FBMC), non-orthogonal multiple access (NOMA),and sparse code multiple access (SCMA) as an advanced access technologyhave been developed.

The Internet, which is a human centered connectivity network wherehumans generate and consume information, is now evolving to the Internetof Things (IoT) where distributed entities, such as things, exchange andprocess information without human intervention. The Internet ofEverything (IoE), which is a combination of the IoT technology and theBig Data processing technology through connection with a cloud server,has emerged. As technology elements, such as “sensing technology”,“wired/wireless communication and network infrastructure”, “serviceinterface technology”, and “Security technology” have been demanded forIoT implementation, a sensor network, a Machine-to-Machine (M2M)communication, Machine Type Communication (MTC), and so forth have beenrecently researched. Such an IoT environment may provide intelligentInternet technology services that create a new value to human life bycollecting and analyzing data generated among connected things. IoT maybe applied to a variety of fields including smart home, smart building,smart city, smart car or connected cars, smart grid, health care, smartappliances and advanced medical services through convergence andcombination between existing Information Technology (IT) and variousindustrial applications.

In line with this, various attempts have been made to apply 5Gcommunication systems to IoT networks. For example, technologies such asa sensor network, Machine Type Communication (MTC), andMachine-to-Machine (M2M) communication may be implemented bybeamforming, MIMO, and array antennas. Application of a cloud RadioAccess Network (RAN) as the above-described Big Data processingtechnology may also be considered to be as an example of convergencebetween the 5G technology and the IoT technology.

According to the recent development of communication systems, variousresearch has progressed on uplink data compression (UDC), and animprovement for preventing uplink and downlink data loss is required.

The above information is presented as background information only toassist with an understanding of the disclosure. No determination hasbeen made, and no assertion is made, as to whether any of the abovemight be applicable as prior art with regard to the disclosure.

SUMMARY

In downlink transmission of a wireless communication system, a highfrequency band and wide bandwidth are used and thus more transmissionresources can be ensured. In addition, in a base station, more antennascan be physically installed and used, and thus beamforming gain and highsignal strength may be obtained. Therefore, a base station can load moredata on the same frequency/time resources and then transmit the same toa terminal through a downlink. However, in a case of the uplinktransmission, a terminal has a physically small size, and it isdifficult to use high frequency band and wide bandwidth as the uplinkfrequency. Therefore, uplink transmission resources may have bottleneckscompared to downlink transmission resources. In addition, a terminal hasmaximum transmission power much smaller than that of a base station, andthus has also a problem in that the coverage is small when transmittinguplink data. Therefore, transmission resources are required to beefficiently used through compression of uplink data.

Aspects of the disclosure are to address at least the above-mentionedproblems and/or disadvantages and to provide at least the advantagesdescribed below. Accordingly, an aspect of the disclosure is to providean apparatus and a method for compressing uplink data employs a schemeof successively compressing data, based on previous data. Therefore, ifone piece of data among a series of pieces of compressed data is lost ordiscarded, or fails to be decompressed, a reception node fails todecompress all the data after the piece of data that is lost ordiscarded, or fails to be decompressed.

A transmission node packet data convergence protocol (PDCP) layer devicemay: drive a PDCP discard timer for each data every time when data isreceived from an upper layer device, perform an uplink compressionprocess if the uplink compression process is configured, configure a UDCheader, encode data to which uplink data compression has been performed,and assign a PDCP sequence number and configure a PDCP header togenerate a PDCP protocol data unit (PDCP PDU). If the PDCP discard timerhas expired, data corresponding to the timer is assumed as not beingvalid any more, and then discarded.

Therefore, if a transmission PDCP layer device has discarded previouslygenerated data (e.g., PDCP PDU) due to the expiration of the PDCPdiscard timer, particular data is discarded among a series of pieces ofcompressed data. Therefore, a reception PDCP layer device may fail insuccessive data decompression due to the discard or loss of thecompressed data.

Additional aspects will be set forth in part in the description whichfollows and, in part, will be apparent from the description, or may belearned by practice of the presented embodiments.

In accordance with an aspect of the disclosure, a method performed by atransmitting device is provided. The method includes receiving, from areceiving device, a packet data convergence protocol (PDCP) controlprotocol data unit (PDU) including information indicating a check sumfailure, discarding a first PDCP PDU based on the information, the firstPDCP PDU not being submitted to a lower layer and PDCP processing beingperformed for, delivering a first indicator to the lower layer, thefirst indicator indicating a discard of data which was delivered to thelower layer, performing a first PDCP processing for a PDCP service dataunit (SDU) corresponding to the first PDCP PDU, and transmitting, to thereceiving device, a second PDCP PDU generated based on the first PDCPprocessing.

In accordance with another aspect of the disclosure, a method performedby a receiving device is provided. The method includes identifying thata check sum failure has occurred, transmitting, to a transmittingdevice, a packet data convergence protocol (PDCP) control protocol dataunit (PDU) including information indicating the check sum failure,receiving, from the transmitting device, a first PDCP PDU aftertransmitting of the PDCP control PDU, and discarding at least one PDCPPDU from the first PDCP PDU, wherein a PDCP header of the discarded atleast one PDCP PDU does not include a first indicator indicating a resetof a uplink data compression (UDC) buffer of the transmitting device.

In accordance with another aspect of the disclosure, a transmittingdevice is provided. The transmitting device includes a transceiverconfigured to transmit and receive a signal, and a controller configuredto: receive, from a receiving device, a packet data convergence protocol(PDCP) control protocol data unit (PDU) including information indicatinga check sum failure, discard a first PDCP PDU based on the information,the first PDCP PDU not being submitted to a lower layer and PDCPprocessing being performed for, deliver a first indicator to the lowerlayer, the first indicator indicating a discard of data which wasdelivered to the lower layer, perform a first PDCP processing for a PDCPservice data unit (SDU) corresponding to the first PDCP PDU, andtransmit, to the receiving device, a second PDCP PDU generated based onthe first PDCP processing.

In accordance with another aspect of the disclosure, a receiving deviceis provided. The receiving device includes a transceiver configured totransmit and receive a signal, and a controller configured to: identifythat a check sum failure has occurred, transmit, to a transmittingdevice, a packet data convergence protocol (PDCP) control protocol dataunit (PDU) including information indicating the check sum failure,receive, from the transmitting device, a first PDCP PDU aftertransmitting of the PDCP control PDU, and discard at least one PDCP PDUfrom the first PDCP PDU, wherein a PDCP header of the discarded at leastone PDCP PDU does not include a first indicator indicating a reset of auplink data compression (UDC) buffer of the transmitting device.

In accordance with another aspect of the disclosure, a process in whichwhen a transmission PDCP layer device (terminal or base station)transmits data through uplink or downlink in a wireless communicationsystem is provided. The transmission PDCP layer device compresses andtransmits the data and a reception PDCP layer device (base station orterminal) receives and decompresses the data.

In accordance with another aspect of the disclosure, a method forsupporting a data transmission/reception process in which a transmissionnode is provided. The method compresses and transmits data and areception node decompresses the data, the method including a specificheader format, a solution of decompression failure, and a solution ofdiscarding by a PDCP discard timer in a transmission PDCP layer device.In addition, a proposed embodiment may be also applied to a process inwhich when a base station transmits downlink data to a terminal, thebase station compresses and transmits the data and the terminal receivesand decompresses the compressed downlink data. As described above, inthe disclosure, a transmission node compresses and transmits data, andthus can transmit more data and improve the coverage at the same time.

In addition, if an uplink data compression (UDC) process is configured,a transmission PDCP layer device performs a data compression process onpieces of data received from an upper layer device, and then stores thepieces of data to transmit same when an uplink transmission resource isreceived. In this situation, if data having been subjected to UDCcompression and having not been transmitted yet is discarded due to theexpiration of a PDCP discard timer, a reception PDCP layer device failson UDC decompression of pieces of data having been subjected to UDCcompression among pieces of data each having a PDCP sequence numberlarger than that of the discarded data, and thus all the pieces of dataare lost. Therefore, the disclosure proposes a solution for solving theproblem.

Other aspects, advantages, and salient features of the disclosure willbecome apparent to those skilled in the art from the following detaileddescription, which, taken in conjunction with the annexed drawings,discloses various embodiments of the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages, reference ofcertain embodiments of the disclosure will be more apparent from thefollowing description taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a diagram illustrating a structure of an LTE system accordingto an embodiment of the disclosure;

FIG. 2 is a diagram illustrating a wireless protocol structure of an LTEsystem to which the disclosure may be applied according to an embodimentof the disclosure;

FIG. 3 is a diagram illustrating a structure of a next generation mobilecommunication system according to an embodiment of the disclosure;

FIG. 4 is a diagram illustrating a wireless protocol structure of a nextgeneration mobile communication system according to an embodiment of thedisclosure;

FIG. 5 is a diagram illustrating a process of configuring whether a basestation is to perform uplink data compression, when a terminalconfigures a connection with a network according to an embodiment of thedisclosure;

FIG. 6 is a diagram illustrating a data configuration and a process ofperforming uplink data compression according to an embodiment of thedisclosure;

FIG. 7 is a diagram illustrating an embodiment of an uplink datacompression method which may be applied according to an embodiment ofthe disclosure;

FIG. 8 is a diagram illustrating a problem in which a decompressionfailure occurs in an uplink data compression method according to anembodiment of the disclosure;

FIG. 9 illustrates a PDCP control PDU format which may be applied in achecksum failure processing method according to an embodiment of thedisclosure;

FIG. 10 is a diagram illustrating a terminal operation performed when atransmission node PDCP layer device drives a PDCP discard timer and datahaving not been transmitted yet and having been subjected to UDC isdiscarded due to an expiration of the PDCP discard timer according to anembodiment of the disclosure;

FIG. 11 is a diagram illustrating a (2-1)th embodiment in which a userdata compression method is efficiently performed in a case where an SDAPlayer device or an SDAP header is configured through an RRC messageaccording to an embodiment of the disclosure;

FIG. 12 is a diagram illustrating a (2-2)th embodiment in which a userdata compression method is efficiently performed in a case where an SDAPlayer device or an SDAP header is configured through an RRC messageaccording to an embodiment of the disclosure;

FIG. 13 is a diagram illustrating a (2-3)th embodiment in which a userdata compression method is efficiently performed in a case where an SDAPlayer device or an SDAP header is configured through an RRC messageaccording to an embodiment of the disclosure;

FIG. 14 is a diagram illustrating a (2-4)th embodiment in which a userdata compression method is efficiently performed in a case where an SDAPlayer device or an SDAP header is configured through an RRC messageaccording to an embodiment of the disclosure;

FIG. 15 is a diagram illustrating a (2-5)th embodiment in which a userdata compression method is efficiently performed in a case where an SDAPlayer device or an SDAP header is configured through an RRC messageaccording to an embodiment of the disclosure;

FIG. 16 is a diagram illustrating a (2-6)th embodiment in which a userdata compression method is efficiently performed in a case where an SDAPlayer device or an SDAP header is configured through an RRC messageaccording to an embodiment of the disclosure;

FIG. 17 is a diagram illustrating a terminal operation proposedaccording to an embodiment of the disclosure;

FIG. 18 illustrates a structure of a terminal to which an embodiment maybe applied according to an embodiment of the disclosure; and

FIG. 19 illustrates a block configuration of a base station (ortransmission and reception point (TRP)) in a wireless communicationsystem to which an embodiment may be applied according to an embodimentof the disclosure.

Throughout the drawings, like reference numerals will be understood torefer to like parts, components, and structures.

DETAILED DESCRIPTION

The following description with reference to the accompanying drawings isprovided to assist in a comprehensive understanding of variousembodiments of the disclosure as defined by the claims and theirequivalents. It includes various specific details to assist in thatunderstanding but these are to be regarded as merely exemplary.Accordingly, those of ordinary skill in the art will recognize thatvarious changes and modifications of the various embodiments describedherein can be made without departing from the scope and spirit of thedisclosure. In addition, descriptions of well-known functions andconstructions may be omitted for clarity and conciseness.

The terms and words used in the following and claims are not limited tothe bibliographical meanings, but, are merely used by the inventor toenable a clear and consistent understanding of the disclosure.Accordingly, it should be apparent to those skilled in the art that thefollowing description of various embodiments of the disclosure isprovided for illustration purpose only and not for the purpose oflimiting the disclosure as defined by the appended claims and theirequivalents.

It is to be understood that the singular forms “a,” “an,” and “the”include plural referents unless the context clearly dictates otherwise.Thus, for example, reference to “a component surface” includes referenceto one or more of such surfaces.

For the same reason, in the accompanying drawings, some elements may beexaggerated, omitted, or schematically illustrated. Further, the size ofeach element does not entirely reflect the actual size. In the drawings,identical or corresponding elements are provided with identicalreference numerals.

The advantages and features of the disclosure and ways to achieve themwill be apparent by making reference to embodiments as described belowin detail in conjunction with the accompanying drawings. However, thedisclosure is not limited to the embodiments set forth below, but may beimplemented in various different forms. The following embodiments areprovided only to make the disclosure complete and clearly inform thoseskilled in the art of the scope of the disclosure, and the disclosure isdefined only by the scope of the appended claims. Throughout thespecification, the same reference numerals designate the same elements.

Here, it will be understood that each block of the flowchartillustrations, and combinations of blocks in the flowchartillustrations, can be implemented by computer program instructions.These computer program instructions can be provided to a processor of ageneral purpose computer, special purpose computer, or otherprogrammable data processing apparatus, such that the instructions,which execute via the processor of the computer or other programmabledata processing apparatus, create means for implementing the functionsspecified in the flowchart block(s). These computer program instructionsmay also be stored in a computer usable or computer-readable memory thatcan direct a computer or other programmable data processing apparatus tofunction in a particular manner, such that the instructions stored inthe computer usable or computer-readable memory produce an article ofmanufacture including instruction means that implement the functionspecified in the flowchart block(s). The computer program instructionsmay also be loaded onto a computer or other programmable data processingapparatus to cause a series of operations to be performed on thecomputer or other programmable data processing apparatus to produce acomputer implemented process such that the instructions that execute onthe computer or other programmable data processing apparatus provideoperations for implementing the functions specified in the flowchartblock(s).

Each block of the flowchart illustrations may represent a module,segment, or portion of code, which includes one or more executableinstructions for implementing the specified logical function(s). Itshould also be noted that in some alternative implementations, thefunctions noted in the blocks may occur out of order. For example, twoblocks shown in succession can in fact be executed substantiallyconcurrently or the blocks can sometimes be executed in the reverseorder, depending upon the functionality involved.

As used herein, the “unit” or “module” refers to a software element or ahardware element, such as a field programmable gate array (FPGA) or anapplication specific integrated circuit (ASIC), which performs apredetermined function. However, the “unit” or “module” does not alwayshave a meaning limited to software or hardware. The “unit” or “module”may be constructed either to be stored in an addressable storage mediumor to execute one or more processors. Therefore, the “unit” or “module”includes, for example, software elements, object-oriented softwareelements, class elements or task elements, processes, functions,properties, procedures, sub-routines, segments of a program code,drivers, firmware, micro-codes, circuits, data, database, datastructures, tables, arrays, and parameters. The elements and functionsprovided by the “unit” or “module” may be either combined into a smallernumber of elements, “unit”, or “module” or divided into a larger numberof elements, “unit”, or “module”. Moreover, the elements and “units” or“modules” may be implemented to reproduce one or more CPUs within adevice or a security multimedia card.

Hereinafter, the operating principle of the disclosure will be describedin detail with reference to the accompanying drawings. In describing thedisclosure below, a detailed description of related known configurationsor functions incorporated herein will be omitted when it is determinedthat the detailed description thereof may unnecessarily obscure thesubject matter of the disclosure. The terms as described below aredefined in consideration of the functions in the disclosure, and themeaning of the terms may vary according to the intention of a user oroperator, convention, or the like. Therefore, the definitions of theterms should be made based on the contents throughout the specification.

In describing the disclosure below, a detailed description of relatedknown configurations or functions incorporated herein will be omittedwhen it is determined that the detailed description thereof mayunnecessarily obscure the subject matter of the disclosure. Hereinafter,embodiments will be described with reference to the accompanyingdrawings.

In the following description, a term for identifying an access node,terms for indicating network entities, terms for indicating messages, aterm for indicating an interface between network entities, terms forindicating various identification information, and the like are examplesfor convenience of explanation. Therefore, the disclosure may not belimited by the terminologies provided below, and other terms thatindicate subjects having equivalent technical meanings may be used.

For convenience of description, terms and names defined in 3rdgeneration partnership project (3GPP) LTE standards will be used in thedisclosure. However, the disclosure is not limited to the terms andnames, and may be applied to a system following other standards in thesame way. In the disclosure, an evolved node B (eNB) may be usedtogether with a next generation node B (gNB) for convenience ofexplanation. That is, a base station described as an eNB may indicate agNB.

FIG. 1 is a diagram illustrating a structure of an LTE system accordingto an embodiment of the disclosure.

Referring to FIG. 1, as illustrated, a wireless access network of an LTEsystem includes next generation base stations (an ENB, a Node B, or abase station) 1-05, 1-10, 1-15, and 1-20, a mobility management entity(MME) 1-25, and a serving gateway (S-GW) 1-30. A user equipment(hereinafter, UE or terminal) 1-35 accesses an external network throughthe ENBs 1-05 to 1-20 and the S-GW 1-30.

In FIG. 1, the ENBs 1-05 to 1-20 correspond to a node B of a universalmobile telecommunication system (UMTS). An ENB is connected to the UE1-35 through a wireless channel and performs complex functions comparedto a node B. In the LTE system, all the user traffic including real-timeservice such as a voice over IP (VoIP) through an Internet protocol isserviced through a shared channel Therefore, the LTE system requires adevice configured to collect pieces of state information including abuffer state, an available transmission power state, and a channel stateof UEs and perform scheduling, and the ENBs 1-05 to 1-20 serves as thedevice. One ENB generally controls a plurality of cells. For example, aLTE system uses, as a wireless access technology, for example,orthogonal frequency division multiplexing (hereinafter, referred to asOFDM) in a bandwidth of 20 MHz in order to implement a transfer rate of100 Mbps. Further, an adaptive modulation and coding (hereinafter,referred to as an AMC) scheme for determining a modulation scheme and achannel coding rate according to a channel state of a terminal isemployed. The S-GW 1-30 is a device configured to provide a data bearer,and generates or removes a data bearer according to a control of the MME1-25. The MME is an apparatus which is responsible for various controlfunctions as well as a mobility management function for a terminal, andis connected to a plurality of base stations.

FIG. 2 is a diagram illustrating a wireless protocol structure of an LTEsystem according to an embodiment of the disclosure.

Referring to FIG. 2, a wireless protocol of an LTE system includes apacket data convergence protocol (PDCP) 2-05 or 2-40, a radio linkcontrol (RLC) 2-10 or 2-35, and a medium access control (MAC) 2-15 or2-30 in each of a terminal and an ENB. The packet data convergenceprotocol (PDCP) 2-05 or 2-40 is configured to perform an operation ofcompressing/reconstructing an IP header. Main functions of the PDCP aresummarized as below.

-   -   Header compression and decompression (ROHC only)    -   Transfer of user data    -   In-sequence delivery (In-sequence delivery of upper layer PDUs        at PDCP re-establishment procedure for RLC AM)    -   Reordering (For split bearers in DC (only support for RLC AM):        PDCP PDU routing for transmission and PDCP PDU reordering for        reception)    -   Duplicate detection (Duplicate detection of lower layer service        data units (SDUs) at PDCP re-establishment procedure for RLC AM)    -   Retransmission (Retransmission of PDCP SDUs at handover and, for        split bearers in DC, of PDCP PDUs at PDCP data-recovery        procedure, for RLC AM)    -   Ciphering and deciphering    -   Timer-based SDU discard (Timer-based SDU discard in uplink)

The radio link control (hereinafter, referred to as RLC) 2-10 or 2-35reconfigures a PDCP protocol data unit (PDCP PDU) to have a proper sizeand then performs an automatic repeat request (ARQ) operation. Mainfunctions of the RLC are summarized as below.

-   -   Data transfer (Transfer of upper layer PDUs)    -   ARQ (Error Correction through ARQ (only for acknowledged mode        (AM) data transfer))    -   Concatenation, segmentation, and reassembly (Concatenation,        segmentation, and reassembly of RLC SDUs (only for        unacknowledged mode (UM) and AM data transfer))    -   Re-segmentation (Re-segmentation of RLC data PDUs (only for AM        data transfer))    -   Reordering (Reordering of RLC data PDUs (only for UM and AM data        transfer)    -   Duplicate detection (Duplicate detection (only for UM and AM        data transfer))    -   Error detection (Protocol error detection (only for AM data        transfer))    -   RLC SDU (only for UM and AM data transfer)    -   RLC re-establishment

The MAC 2-15 or 2-30 is connected to several RLC layer devicesconfigured in a single terminal, multiplexes RLC PDUs to a MAC PDU, anddemultiplexes a MAC PDU to RLC PDUs. Main functions of the MAC aresummarized as below.

-   -   Mapping (Mapping between logical channels and transport        channels)    -   Multiplexing and demultiplexing (Multiplexing/demultiplexing of        MAC SDUs belonging to one or different logical channels        into/from transport blocks (TB) delivered to/from the physical        layer on transport channels)    -   Scheduling information reporting    -   HARQ (Error correction through HARQ (hybrid ARQ))    -   Priority handling between logical channels (Priority handling        between logical channels of one UE)    -   Priority handling between UEs (Priority handling between UEs by        means of dynamic scheduling)    -   Multimedia broadcast multicast services (MBMS) identification    -   Transport format selection    -   Padding

A physical layer 2-20 or 2-25 performs channel coding and modulation onupper layer data to make the data into an OFDM symbol and transmit theOFDM symbol through a wireless channel, or performs demodulation andchannel decoding on an OFDM symbol received through a wireless channel,and then transfers the OFDM symbol to an upper layer.

FIG. 3 is a diagram illustrating a structure of a next generation mobilecommunication system according to an embodiment of the disclosure.

Referring to FIG. 3, as illustrated, a wireless access network of a nextgeneration mobile communication system (hereinafter, NR or 5G) includesa next generation base station (new radio node B, hereinafter, NR gNB orNR base station) 3-10 and a new radio core network (NR CN) 3-05. A userterminal (new radio user equipment, hereinafter, NR UE or terminal) 3-15accesses an external network through a NR gNB 3-10 and the NR CN 3-05.

In FIG. 3, the NR gNB 3-10 corresponds to an evolved node B (eNB) of aLTE system. The NR gNB 3-10 is connected to the NR UE 3-15 through awireless channel 3-20 and may provide an outstanding service compared toa node B. In the NR system, all the user traffic is serviced thoroughshared channels. Therefore, the NR system requires a device configuredto collect pieces of state information including a buffer state, anavailable transmission power state, and a channel state of UEs andperform scheduling, and the NR NB 3-10 serves as the device. One NR gNBgenerally controls a plurality of cells. In order to implementvery-high-speed data transfer compared to the current LTE, the NR gNBmay have a bandwidth wider than the maximum bandwidth, may employorthogonal frequency division multiplexing (OFDM) as a wireless accesstechnology, and a beamforming technology may be additionally integratedtherewith. Further, an adaptive modulation and coding (AMC) scheme fordetermining a modulation scheme and a channel coding rate according to achannel state of a terminal is employed. The NR CN 3-05 performsfunctions such as mobility support, bearer configuration, and quality ofservice (QoS) configuration. The NR CN is an apparatus which isresponsible for various control functions as well as a mobilitymanagement function for a terminal, and is connected to a plurality ofbase stations. Also, the NR system may be also linked to an existing LTEsystem, and the NR CN is connected to an MME 3-25 through a networkinterface. The MME is connected to an eNB 3-30 that is an existing basestation.

FIG. 4 is a diagram illustrating a wireless protocol structure of a nextgeneration mobile communication system according to an embodiment of thedisclosure.

Referring to FIG. 4, a wireless protocol of a next generation mobilecommunication system (NR system) includes a NR PDCP 4-05 or 4-40, an NRRLC 4-10 or 4-35, and an NR MAC 4-15 or 4-30 in each of a terminal andan NR base station. Main functions of the NR PDCP 4-05 or 4-40 mayinclude a part of functions below.

-   -   Header compression and decompression (ROHC only)    -   Transfer of user data    -   In-sequence delivery (In-sequence delivery of upper layer PDUs)    -   Out-of-sequence delivery (Out-of-sequence delivery of upper        layer PDUs)    -   Reordering (PDCP PDU reordering for reception)    -   Duplicate detection (Duplicate detection of lower layer SDUs)    -   Retransmission (Retransmission of PDCP SDUs)    -   Ciphering and deciphering    -   Timer-based SDU discard (Timer-based SDU discard in uplink)

The reordering function of the NR PDCP device may indicate a function ofrearranging PDCP PDUs received from a lower layer, in an order based ona PDCP sequence number (SN). Further, the reordering function mayinclude a function of transferring data to an upper layer according to arearranged order, or may include a function of directly transferringdata without considering order, may include a function of rearranging anorder to record lost PDCP PDUs, may include a function of reporting thestate of lost PDCP PDUs to a transmission side, and may include afunction of requesting retransmission of lost PDCP PDUs.

Main functions of the NR RLC 4-10 or 4-35 may include a part offunctions below.

-   -   Data transfer (Transfer of upper layer PDUs)    -   In-sequence delivery (In-sequence delivery of upper layer PDUs)    -   Out-of-sequence delivery (Out-of-sequence delivery of upper        layer PDUs)    -   ARQ (Error correction through ARQ)    -   Concatenation, segmentation and reassembly (Concatenation,        segmentation and reassembly of RLC SDUs)    -   Re-segmentation (Re-segmentation of RLC data PDUs)    -   Reordering (Reordering of RLC data PDUs)    -   Duplicate detection    -   Error detection (Protocol error detection)    -   RLC SDU discard    -   RLC re-establishment

The in-sequence delivery function of the NR RLC device may indicate afunction of transferring RLC SDUs received from a lower layer, to anupper layer in an order. Furthermore, the in-sequence delivery functionmay include a function of, if one original RLC SDU is divided intoseveral RLC SDUs and then the RLC SDUs are received, reassembling theseveral RLC SDUs and transferring the reassembled RLC SDUs; may includea function of rearranging received RLC PDUs with reference to a RLCsequence number (SN) or a PDCP sequence number (SN); may include afunction of rearranging an order to record lost RLC PDUs; may include afunction of reporting the state of lost RLC PDUs to a transmission side;and may include a function of requesting retransmission of lost RLCPDUs. Moreover, the in-sequence delivery function may include a functionof, if there is a lost RLC SDU, transferring only RLC SDUs before thelost RLC SDU, to an upper layer in an order; may include a function of,although there is a lost RLC SDU, if a predetermined timer is expired,transferring all the RLC SDUs received before the timer is started, toan upper layer in an order; or may include a function of although thereis a lost RLC SDU, if a predetermined timer is expired, transferring allthe RLC SDUs received up to the current, to an upper layer in an order.In addition, the NR RLC device may process RLC PDUs in a reception order(i.e., an order in which the RLC PDUs have arrived, regardless of anorder based on a sequence number (SN)) and then transfer the processedRLC PDUs to a PDCP device regardless of the order (out-of-sequencedelivery). In a case of segments, the NR RLC device may receive segmentsstored in a buffer or to be received in the future, reconfigure thesegments to be one whole RLC PDU, then process the RLC PDU, and transferthe processed RLC PDU to a PDCP device. The NR RLC layer may not includea concatenation function, and the concatenation function may beperformed in an NR MAC layer or replaced with a multiplexing function ofan NR MAC layer.

The out-of-sequence delivery function of the NR RLC device may mean afunction of directly transferring RLC SDUs received from a lower layer,to an upper layer regardless of an order. Furthermore, theout-of-sequence delivery function may include a function of, if oneoriginal RLC SDU is divided into several RLC SDUs and then the RLC SDUsare received, reassembling the several RLC SDUs and transferring thereassembled RLC SDUs; and may include a function of storing a RLCsequence number (SN) or a PDCP sequence number (SN) of received RLC PDUsand arranging an order to record lost RLC PDUs.

The NR MAC 4-15 or 4-30 may be connected to several NR RLC layer devicesconfigured in a single terminal, and main functions of the NR MAC mayinclude a part of functions below.

-   -   Mapping (Mapping between logical channels and transport        channels)    -   Multiplexing and demultiplexing (Multiplexing/demultiplexing of        MAC SDUs)    -   Scheduling information reporting    -   HARQ (Error correction through HARQ)    -   Priority handling between logical channels (Priority handling        between logical channels of one UE)    -   Priority handling between UEs (Priority handling between UEs by        means of dynamic scheduling)    -   MBMS service identification    -   Transport format selection    -   Padding

An NR physical (PHY) layer 4-20 or 4-25 may perform channel coding andmodulation on upper layer data to make the data into an OFDM symbol andtransmit the OFDM symbol through a wireless channel, or may performdemodulation and channel-decoding on an OFDM symbol received through awireless channel, and then transfer the OFDM symbol to an upper layer.

The disclosure proposes a process in which when a terminal (or atransmission node) transmits data through uplink in a wirelesscommunication system, the terminal compresses the data and a basestation (or a reception node) decompresses the data. In addition, thedisclosure proposes a method for supporting a datatransmission/reception process in which a transmission node compressesdata and a reception node decompresses the data, the method including aspecific header format and a solution of decompression failure. Inaddition, a method proposed in the disclosure may be also applied to aprocess in which when a base station (or a transmission node) transmitsdownlink data to a terminal (or a reception node), the base stationcompresses and transmits the data and the terminal receives anddecompresses the compressed downlink data. As described above, in thedisclosure, a transmission node compresses and transmits data, and thuscan transmit more data and improve the coverage at the same time.

FIG. 5 is a diagram illustrating a process of configuring whether a basestation is to perform uplink data compression, when a terminalconfigures a connection with a network according to an embodiment of thedisclosure.

FIG. 5 illustrates a process in which a terminal switches a radioresource control (RRC) idle mode or an RRC inactive mode (orlightly-connected mode) to an RRC connected mode and configures aconnection with a network, and illustrates a process in the terminalconfigures whether to perform uplink data compression (UDC), in thedisclosure.

Referring to FIG. 5, if a terminal that transmits or receives data in anRRC connected mode does not perform transmission or reception of datadue to a predetermined reason or during a predetermined time interval, abase station may transmit an RRCConnectionRelease message to theterminal to allow the terminal to be switched to an RRC idle mode(operation 5-01). In the future, the terminal (hereinafter, idle modeUE) in which a current connection is not configured performs an RRCconnection establishment procedure with the base station if data to betransmitted occurs. The terminal establishes reverse transmissionsynchronization with the base station through a random access procedureand transmits an RRCConnectionRequest message to the base station(operation 5-05). The message contains an identifier of the terminal anda cause (establishmentCause) of connection configuration.

The base station transmits an RRCConnectionSetup message to the terminalso that the terminal configures an RRC connection (operation 5-10). Themessage may include information indicating whether to use an uplink datacompression method (UDC) or whether to use a downlink data compressionmethod for each logical channel (logicalchannelconfig), each bearer, oreach PDCP device (PDCP-config). In addition, the message may morespecifically indicate only a IP flow or a QoS flow for which an uplinkdata compression method (UDC) is to be used in each logical channel,each bearer, or each PDCP device (or service data adaptation protocol(SDAP) device) (e.g., the message may configure, for an SDAP device,information relating to an IP flow or a QoS flow for which an uplinkdata compression method is used or not used, so that the SDAP device mayindicate, to a PDCP device, whether to use an uplink data compressionmethod for each QoS flow. Otherwise, a PDCP device may identify each QoSflow by itself and determine whether to apply an uplink compressionmethod).

In addition, in the above description, if use of an uplink datacompression method is indicated, the message may indicate a predefinedlibrary to be used in the uplink data compression method, an identifierof dictionary information (Dictionary), or a buffer size to be used inthe uplink data compression method. In addition, the message may includea command which sets up or releases performing of uplink decompression.In addition, in the above description, when use of an uplink datacompression method is configured, an RLC AM bearer (a mode in whichthere are an ARQ function and a retransmission function and thus thereis no loss) may be configured every time, and a header compressionprotocol (ROHC) may not be configured together.

In addition, the message contains RRC connection configurationinformation. An RRC connection is also called a signaling radio bearer(SRB), and is used for transmission and reception of an RRC message thatis a control message between the terminal and the base station. Theterminal having configured the RRC connection transmits anRRCConnetionSetupComplete message to the base station (operation 5-15).If the base station does not know terminal capability of the terminalconfiguring the current connection or desires to identify the terminalcapability, the base station may transmit a message asking thecapability of the terminal. The terminal may transmit a messagereporting terminal capability. The message of the terminal reporting theterminal capability may indicate whether the terminal can use an uplinkdata compression method (UDC) or a downlink data compression method, andmay be transmitted with an indicator indicating same.

The RRCConnetionSetupComplete message includes a control message, calledSERVICE REQUEST, through which the terminal requests bearerconfiguration for a predetermined service from an MME. The base stationtransmits the SERVICE REQUEST message contained in theRRCConnetionSetupComplete message to the MME (operation 5-20), and theMME determines whether to provide the service requested by the terminal.If a result of the determination shows that the MME has decided toprovide the service requested by the terminal, the MME transmits anINITIAL CONTEXT SETUP REQUEST message to the base station (operation5-25). The message includes information such as quality-of-service (QoS)information to be applied at the time of configuration of a data radiobearer (DRB), and security-related information (e.g., Security Key,Security Algorithm) to be applied to the DRB.

The base station exchanges a SecurityModeCommand message (operation5-30) and a SecurityModeComplete message (5-35) in order to configuresecurity with the terminal. If the configuring of the security iscompleted, the base station transmits an RRCConnectionReconfigurationmessage to the terminal (operation 5-40). The message may includeinformation indicating whether to use an uplink data compression method(UDC) or whether to use a downlink data compression method for eachlogical channel (logicalchannelconfig), each bearer, or each PDCP device(PDCP-config). In addition, the message may more specifically indicateonly a IP flow or a QoS flow for which an uplink data compression method(UDC) is to be used in each logical channel, each bearer, or each PDCPdevice (or SDAP device) (e.g., the message may configure, for an SDAPdevice, information relating to an IP flow or a QoS flow for which anuplink data compression method is used or not used, so that the SDAPdevice may indicate, to a PDCP device, whether to use an uplink datacompression method for each QoS flow. Otherwise, a PDCP device mayidentify each QoS flow by itself and determine whether to apply anuplink compression method).

In addition, in the above description, if use of an uplink datacompression method is indicated, the message may indicate a predefinedlibrary to be used in the uplink data compression method, an identifierof dictionary information (Dictionary), or a buffer size to be used inthe uplink data compression method. In addition, the message may includea command which sets up or releases performing of uplink decompression.In addition, in the above description, when use of an uplink datacompression method is configured, an RLC AM bearer (a mode in whichthere are an ARQ function and a retransmission function and thus thereis no loss) may be configured every time, and a header compressionprotocol (ROHC) may not be configured together.

In addition, the message includes configuration information of a DRBthrough which user data is processed, and the terminal configures theDRB by applying the information and transmits anRRCConnectionReconfigurationComplete message to the base station(operation 5-45). The base station having completed the configuring ofthe DRB with the terminal transmits an INITIAL CONTEXT SETUP COMPLETEmessage to the MME (operation 5-50), and the MME having received themessage exchanges an S1 BEARER SETUP message and an S1 BEARER SETUPRESPONSE message in order to configure a S1 bearer with an S-GW(operations 5-55 and 5-60). The S1 bearer is a data transmissionconnection configured between the S-GW and the base station andcorresponds to the DRB in one-to-one correspondence. If all theprocedures are completed, the terminal transmits or receives data to orfrom the base station through the S-GW (operations 5-65 and 5-70).

As described above, a general data transmission procedure generallyincludes three stages of RRC connection configuration, securityconfiguration, and DRB configuration. In addition, the base station maytransmit an RRCConnectionReconfiguration message to newly establish aconfiguration, add a configuration, or change a configuration for theterminal due to a predetermined reason (operation 5-75). The message mayinclude information indicating whether to use an uplink data compressionmethod (UDC) or whether to use a downlink data compression method foreach logical channel (logicalchannelconfig), each bearer, or each PDCPdevice (PDCP-config). In addition, the message may more specificallyindicate only a IP flow or a QoS flow for which an uplink datacompression method (UDC) is to be used in each logical channel, eachbearer, or each PDCP device (or service data adaptation protocol (SDAP)device) (e.g., the message may configure, for an SDAP device,information relating to an IP flow or a QoS flow for which an uplinkdata compression method is used or not used, so that the SDAP device mayindicate, to a PDCP device, whether to use an uplink data compressionmethod for each QoS flow. Otherwise, a PDCP device may identify each QoSflow by itself and determine whether to apply an uplink compressionmethod).

In addition, in the above description, if use of an uplink datacompression method is indicated, a predefined library to be used in theuplink data compression method, an identifier of dictionary information(Dictionary), or a buffer size to be used in the uplink data compressionmethod may be indicated. In addition, the message may include a commandwhich sets up or releases performing of uplink decompression. Inaddition, in the above description, when use of an uplink datacompression method is configured, an RLC AM bearer (a mode in whichthere are an ARQ function and a retransmission function and thus thereis no loss) may be configured every time, and a header compressionprotocol (ROHC) may not be configured together.

FIG. 6 is a diagram illustrating a data configuration and a process ofperforming uplink or downlink data compression according to anembodiment of the disclosure. The following description will be based onuplink data for convenience of explanation, but may be applied todownlink data in the same way.

Referring to FIG. 6, uplink data 6-05 may be generated to be datacorresponding to services such as video transmission, phototransmission, Web search, and VoLTE. Pieces of data generated in anapplication layer device may be processed through a user datagramprotocol (UDP) or a transmission control protocol/Internet protocol(TCP/IP) corresponding to a network data transmission layer, mayconfigure individual headers 6-10 and 6-15, and may be transferred to aPDCP layer. The PDCP layer may perform the following process if the PDCPlayer receives data (PDCP SDU) from an upper layer.

If an uplink data compression method is configured to be used in thePDCP layer by an RRC message, for example, in operation 5-10, 5-40, or5-75 in FIG. 5, the PDCP layer may compress uplink data by performing anuplink data compression (UDC) method on a PDCP SDU, for example, inoperation 6-20; configure a UDC header (header 6-25 for compresseduplink data) corresponding to the compressed data; encode (ciphering)the compressed data 6-35 excluding the UDC header; perform integrityprotection if the integrity protection is configured; and configure aPDCP header 6-30 to configure a PDCP PDU. In the above description, aPDCP layer device includes a UDC compression/decompression device,determines whether to perform a UDC process on each data, according tothe configuration of the RRC message, and uses the UDCcompression/decompression device. In a transmission node, a transmissionPDCP layer device performs data compression by using a UDC compressiondevice, and in a reception node, a reception PDCP layer device performsdata decompression by using a UDC decompression device.

The processes in FIG. 6 described above may be also applied tocompression of downlink data by a base station, as well as compressionof uplink data by a terminal. In addition, the above description aboutuplink data may be also applied to downlink data in the same way.

FIG. 7 is a diagram illustrating an embodiment of an uplink datacompression method which may be applied in the disclosure according toan embodiment of the disclosure.

Referring to FIG. 7, a diagram of an uplink data compression algorithmbased on DEFLATE, and an uplink data compression algorithm based onDEFLATE is a lossless compression algorithm is illustrated. TheDEFLATE-based uplink data compression algorithm basically combines aLZ77 algorithm and Huffman coding to compress uplink data. The LZ77algorithm performs an operation of scanning an overlapping arrangementof data, wherein the scanning of the overlapping arrangement isperformed in a sliding window through the sliding window; and if theoverlapping arrangement is discovered, expresses the position of theoverlapping arrangement and the length of the overlapping amount in thesliding window, to perform data compression. The sliding window is alsocalled a buffer in an uplink data compression (UDC) method, and may beconfigured to have 8 kilobytes or 32 kilobytes. That is, the slidingwindow or a buffer may record 8192 or 32768 characters, scan overlappingarrangements, and express same by using the length and the position toperform compression.

Therefore, the LZ algorithm corresponds to a sliding window scheme, andthus previously coded pieces of data are updated in a buffer, andimmediately subsequent pieces of data are coded again. Therefore,consecutive pieces of data are correlated. Therefore, only if previouslycoded pieces of data are decoded normally, it is possible to normallydecode subsequent pieces of data. In the above description, codes(expression such as position and length) compressed by being expressedthrough the LZ77 algorithm by the position and length are compressedthrough Huffman coding once more. The Huffman coding scans overlappingcodes again and compress the codes once more by using a short mark for acode overlapped many times and using a long mark for a code lessoverlapped. The Huffman coding corresponds to prefix coding, and anoptimal coding scheme having a characteristic (uniquely decodable) inwhich all the codes are clearly distinguished from each other.

As described above, a transmission node may encode raw data 7-05 byapplying a LZ77 algorithm to same (operation 7-10), update a buffer(operation 7-15), and generate checksum bits of contents (or data) ofthe buffer to configure the bits for a UDC header. The checksum bits areused for a reception node to determine whether the state of the bufferis valid. Codes encoded through the LZ77 algorithm may be compressedthrough Huffman (operation 7-20) coding once more and then betransmitted through uplink data (operation 7-25). The reception nodeperforms a decompression process on the received compressed datacontrary to the transmission node. That is, the reception node performsHuffman decoding (operation 7-30), updates a buffer (operation 7-35),and identifies whether the updated buffer is valid, through the checksumbits of the UDC header. If it is determined that there are no errors inthe checksum bits, the reception node may perform decoding through aLZ77 algorithm (operation 7-40) to decompress data and reconstruct theraw data, and transfer the reconstructed data to an upper layer(operation 7-45).

As described above, the LZ algorithm corresponds to a sliding windowscheme, that is, previously coded pieces of data are updated in abuffer, and immediately subsequent pieces of data are coded again.Therefore, consecutive pieces of data are correlated. Therefore, only ifpreviously coded pieces of data are decoded normally, it is possible tonormally decode subsequent pieces of data. Therefore, a reception PDCPlayer device identifies a PDCP sequence number of a PDCP header andidentifies (identifies an indicator indicating whether data compressionhas been performed or not) a UDC header and performs a datadecompression process on pieces of data to which a data compressionprocess has been applied, according to an ascending order based on thePDCP sequence numbers.

A process in which a base station performs uplink data compression (UDC)configuration to a terminal, and a process in a terminal performs uplinkdata compression (UDC), proposed in the disclosure are given as follows.In addition, in the following description, UDC implies an uplink datacompression procedure of a terminal, but may be also applied to adownlink data compression procedure of a base station for the samepurpose. Particularly, although the meaning of the term UDC includesuplink, a compression procedure according to UDC can be also applied todownlink. Plenty of different terms may be applied to downlink insteadof the term UDC.

A base station may configure or release, for a terminal, performing ofuplink data compression on a bearer or a logical channel in which an RLCAM mode is configured, by an RRC message, for example, in operation5-10, 5-40, or 5-75 in FIG. 5. In addition, the base station may reset aUDC device (or protocol) of a PDCP layer device of the terminal by usingthe RRC message. The resetting of the UDC device (or protocol) impliesresetting of a UDC buffer for uplink data compression of the terminal,and is performed to synchronize a UDC buffer of the terminal with a UDCbuffer for uplink data decompression of the base station. The resettingof a buffer of the UDC device may define a new PDCP control PDU so thatthe PDCP control PDU may be used instead of the RRC message to atransmission node (base station) to reset a UDC buffer of a receptionnode (terminal) and perform synchronization for user datacompression/decompression between the transmission node and thereception node. In addition, the base station may configure whetheruplink data compression is performed, for each bearer, each logicalchannel, or each PDCP layer device by using the RRC message. Morespecifically, the base station may configure whether uplink datadecompression is to be performed, for each IP flow (or QoS flow) in abearer, a logical channel, or a PDCP layer device.

In addition, the base station may configure a PDCP discard timer valuefor the terminal by the RRC message. As the PDCP discard timer value, aPDCP discard timer value for data for which uplink data compression isnot performed, and a PDCP discard timer value for data to which uplinkdata compression is applied may be configured separately.

If the terminal is configured to perform uplink data compression on apredetermined bearer, logical channel, or PDCP layer device (or some QoSflows of a predetermined bearer, logical channel, or PDCP layer device)by the RRC message, the terminal resets a buffer in a UDC device of aPDCP layer device according to the configuration, and prepares an uplinkdata compression process. After the preparation, if the terminalreceives data (i.e., PDCP SDU) from an upper layer and is configured toperform uplink data compression on the PDCP layer device, the terminalperforms uplink data compression on the received data. If the terminalis configured to perform uplink data compression on only particular QoSflows of the PDCP layer device, the terminal identifies a QoS flowidentifier or an indication of an upper SDAP layer to determine whetherto perform uplink data compression and then performs uplink datacompression. If the terminal performs uplink data compression (UDC) andupdates a buffer according to the data compression, the terminalconfigures a UDC buffer.

In the above description, if the terminal performs uplink datacompression (UDC), the terminal may compress a PDCP SDU received from anupper layer to be UDC compression data (UDC block) having a smallersize. The terminal configures a UDC header relating to compressed UDCcompression data. The UDC header may include an indicator indicatingwhether uplink data compression has been performed or not (e.g., if aone-bit indicator of the UDC header is 0, this implies UDC has beenapplied, and if the indicator is 1, this implies UDC has beenunapplied).

In the above description, a case where the terminal does not applyuplink data compression may include a case where data compression isunable to be performed by the above described UDC compression method(DEFLATE algorithm) since a PDCP SDU data structure received from anupper layer is not a repetitive data structure. In the abovedescription, if the terminal performs uplink data compression (UDC) ondata (PDCP SDU) received from an upper layer and updates a UDC buffer,the terminal may calculate checksum bits and include same in the UDCbuffer in order to allow a reception PDCP layer device to check thevalidity of the updated UDC buffer (the checksum bits have apredetermined length, and may be configured by 4 bits, for example).

A transmission PDCP layer device (i.e., terminal) may initialize atransmission UDC buffer; and define and configure one bit in a UDCheader of first data to which UDC compression is newly applied after theinitialization of the transmission UDC buffer, to instruct a receptionPDCP layer device to initialize a reception UDC buffer and newly startUDC decompression on the data for which the UDC header is configured,first, to the initialized reception UDC buffer. For example, atransmission PDCP layer device (i.e., terminal) may define a FR field asindicated by reference numeral 9-05 in FIG. 9, and give an indicationthrough the FR field. In addition, whether a transmission PDCP layerdevice in which a UDC compression process is configured as describedabove has applied the UDC compression process to data received from anupper layer may be defined by one bit, for example, an FU field 9-10 inFIG. 9, of the UDC header 9-02 in FIG. 9, and may be indicated throughthe field.

The terminal encodes (ciphering) data to which uplink data decompressionhas been applied or not as described above, performs integrityprotection if the integrity protection is configured, and then transfersthe data to a lower layer.

FIG. 8 is a diagram illustrating a problem in which a decompressionfailure occurs in an uplink or downlink data compression methodaccording to an embodiment of the disclosure.

Referring to FIG. 8, as described above with reference with FIG. 7, analgorithm (DEFLATE algorithm (performing of Huffman coding after LZ77algorithm is performed) performing uplink data compression (UDC) is ascheme in which when a transmission node performs data compression, thetransmission node updates previously compressed data in a buffer,compares the data with data to be compressed next, based on the buffer,scans a repetitive structure, and compresses the structure by positionand length.

Therefore, only if a reception node performs decompression in an orderin which the transmission has performed compression, the decompressionmay succeed. For example, in a case where the transmission node performsUDC compression on pieces of data having PDCP sequence numbers 1, 3, 4,and 5, and does not perform UDC compression on data having PDCP sequencenumber 2 (as indicated by reference numeral 8-05), the reception node isalso required to perform decompression on received data in a PDCP layerdevice in an order of PDCP sequence numbers 1, 3, 4, and 5, tosuccessfully perform the decompression.

If the transmission node performs UDC compression as described above,this performing is indicated by a UDC header, and thus the receptionnode may also determine whether UDC compression is applied, byidentifying the UDC header. If data 8-15 corresponding to PDCP sequencenumber 3 is lost in a procedure of performing a series of UDCdecompression as described above, UDC decompression of data after thedata is failed all. That is, UDC decompression is unable to be performedon pieces of data having PDCP sequence numbers 4 and 5 (as indicated byreference numeral 8-10).

Therefore, there should be no lost data (packet) in an uplinkdecompression process, and the reception node is required to performdecompression in an order in which the transmission node has performedUDC compression on data. Therefore, an RLC AM mode in which there is noloss and there is a retransmission function is required to be operated.

However, loss data described above may be incurred by a PDCP discardtimer of the PDCP layer device. That is, the PDCP layer device drives atimer with a PDCP discard timer value configured by the RRC message foreach data (packet or PDCP SDU) received from an upper layer. If thetimer is expired, the PDCP layer device discards data corresponding tothe timer. Therefore, if a timer of data to which UDC compression hasbeen performed is expired, the data may be discarded, and thus thereception node may fail to perform UDC decompression on pieces ofUDC-compressed data after the data.

As described with reference to FIG. 7 of the disclosure, according to analgorithm (DEFLATE algorithm (performing of Huffman coding after LZ77algorithm is performed)) performing uplink data compression (UDC), whena transmission node performs uplink data compression, uplink datacompression is performed, and then the transmission node generateschecksum by using current buffer contents and configures the checksum ina UDC buffer. The transmission node updates the buffer by using raw dataof compressed data, compares the raw data with data to be compressednext, based on the buffer, scans a repetitive structure, and compressesthe structure by the position and length.

Checksum bits in a UDC header is configured to determine the validity ofa current state of the buffer before a UDC device (or function) of areception PDCP layer device performs data decompression. That is, beforethe reception node performs data decompression, the reception nodeidentifies the validity of a current reception node UDC buffer throughchecksum bits in a UDC header. If there are no checksum errors, thereception node performs data decompression and if there occurs achecksum failure, the reception node does not perform data decompressionand is required to report the checksum failure to the transmission nodeand recover from the failure.

Even when the reception node performs decompression, only if thereception node performs decompression in an order in which thetransmission has performed compression, the decompression may succeed.For example, in a case where the transmission node performs UDCcompression on pieces of data having PDCP sequence numbers 1, 3, 4, and5, and does not perform UDC compression on data having PDCP sequencenumber 2, the reception node is also required to perform decompressionon received data in a PDCP layer device in an order of PDCP sequencenumbers 1, 3, 4, and 5, to successfully perform the decompression. Ifthe transmission node performs UDC compression as described above, thisperforming is indicated by a UDC header, and thus the reception node mayalso determine whether UDC compression is applied, by identifying theUDC header. If a checksum failure has occurred at PDCP sequence number 3in a procedure of performing a series of UDC decompression as describedabove, UDC decompression after the failure may be failed all. That is,UDC decompression is unable to be successfully performed on pieces ofdata having PDCP sequence numbers 4 and 5.

In the following description, the disclosure proposes a checksum failureprocessing method for solving a checksum failure problem describedabove.

FIG. 9 illustrates a PDCP control PDU format which may be applied in achecksum failure processing method of the disclosure according to anembodiment of the disclosure.

Referring to FIG. 9, a D/C field is used to distinguish between normaldata or PDCP layer control information (PDCP control PDU) in a PDCPlayer, and a PDU Type field is used to indicate a type of informationamong pieces of PDCP layer control information described above (seetable 1 below). A one-bit indicator (e.g., FE field) indicating whethera checksum failure has occurred or not may be defined and used as a PDCPcontrol PDU format for feedback in a checksum failure processing methodproposed in the disclosure, as illustrated by reference numeral 9-01. Ifthe value of the one-bit indicator is 0, this may indicate that UDCdecompression is being performed normally. If the value of the one-bitindicator is 1, this may indicate that a checksum failure has occurredduring UDC decompression, and indicating initializing (resetting) of aUDC buffer of a transmission PDCP layer device.

In order to define a format 9-01, reserved values (e.g., 011 or a randomreserved value between 100 and 111) may be assigned to a PDU type todefine a new PDCP control PDU, and a PDCP control PDU having the definedPDU type may serve as a feedback indicating a checksum failure.

TABLE 1 Bit Description 000 PDCP status report 001 Interspersed ROHCfeedback packet 010 LWA status report 011 UDC checksum failure feedback100-111 Reserved

An embodiment proposed in the disclosure, relating to a checksum failureprocessing method to which a PDCP control PDU proposed in FIG. 9 isapplied, is given as follows.

-   -   If a reception node (base station) identifies a checksum failure        of a reception UDC buffer for data to which uplink data        compression (UDC) is to be released, the reception node        transmits a PDCP control PDU to a terminal to indicate that a        checksum failure has occurred. As the PDCP control PDU, a new        PDCP control PDU may be defined and used, and a new indicator        may be defined and then included in an existing PDCP control        PDU, whereby the existing PDCP control PDU may be modified and        used. In another method, an indicator resetting a UDC buffer        since a checksum failure has occurred may be defined instead of        a PDCP sequence number and may indicate the reset.    -   Operation of reception node: If a checksum failure has occurred,        the reception node may initialize the UDC buffer immediately.        The reception node rearranges newly received pieces of data        according to PDCP sequence numbers, and then identifies a UDC        header of each piece of data in an ascending order of the PDCP        sequence numbers. The reception node has received an indicator        showing that a transmission node UDC buffer has been reset due        to a UDC checksum failure, and thus the reception node discards        pieces of data which do not include an indication initializing        the reception UDC buffer and are indicated such that UDC        compression has been performed. In addition, if all the pieces        of data, among newly received pieces of data, which do not        include, in each UDC header, an indicator showing that the        transmission node UDC buffer has been reset due to a UDC        checksum failure, and are indicated such that UDC compression        has not been performed, have been received without a gap        according to an order based on PDCP sequence numbers, the        reception node may process the pieces of data in an ascending        order of the PDCP sequence numbers and then transfer same to an        upper layer device. The reception node may initialize the        reception UDC buffer from pieces of data which include, in each        UDC header, an indicator resetting the reception UDC buffer and        indicating that the transmission node UDC buffer has been reset        due to a UDC checksum failure, and may restart decompression on        UDC-compressed pieces of data in the ascending order of the PDCP        sequence numbers.    -   Operation of transmission node A transmission node (terminal)        may reset (initialize) a UDC transmission buffer if the PDCP        control PDU is received; if there are pieces of data (e.g., PDCP        PDU), among pieces of data generated through a UDC compression        process, which have not been transmitted yet, discard the pieces        of data before the initialization of the UDC transmission        buffer; perform uplink data compression (UDC) again on pieces of        raw data (e.g., PDCP SDU) of the pieces of data which have not        been transmitted yet, based on the initialized transmission UDC        buffer; update the UDC buffer; include checksum bits in a UDC        header; encode the UDC header and data part; generate a PDCP        header; and configure a PDCP PDU to transfer same to a lower        layer. In addition, the transmission node may transfer the UDC        header or the PDCP header of the newly configured PDCP PDU after        including an indicator showing that the transmission node buffer        has been reset and an indication initializing the reception node        buffer, and may newly assign PDCP sequence numbers which have        not been transmitted yet, in an ascending order (That is, if        data which has been encoded with a PDCP sequence number, a HFN,        or a COUNT value and a security key and has been transmitted is        encoded again with the same PDCP COUNT value and the security        key and is then retransmitted, the risk of hacking increases,        and thus a rule in which one PDCP COUNT value allows one time of        encoding and transmission may be followed). In another method,        the transmission node may reset the transmission UDC buffer when        an indication showing that a checksum failure has occurred is        received; newly perform UDC compression only a PDCP PDU to be        newly configured, or data having a PDCP sequence number larger        than or equal to that of data which has not been transmitted yet        to the lower layer from the transmission node; and transfer the        compressed data or PDCP PDU to the lower layer. In addition, the        transmission node may transfer a UDC header or a PDCP header of        the newly configured PDCP PDU after including an indicator        showing that the transmission node UDC buffer has been reset (or        an indicator initializing the reception node buffer)(That is, if        data which has been encoded with a PDCP COUNT value and a        security key and has been transmitted is encoded again with the        same PDCP COUNT value and the security key and is then        retransmitted, the risk of hacking increases, and thus a rule in        which one PDCP COUNT value allows one time of encoding and        transmission may be followed).

However, a checksum failure described above may be incurred by a PDCPdiscard timer of a PDCP layer device. That is, a PDCP layer devicedrives a timer with a PDCP discard timer value configured by the RRCmessage for each data (packet or PDCP SDU) received from an upper layer.If the timer is expired, the PDCP layer device discards datacorresponding to the timer. Therefore, if a timer of pieces of data towhich UDC compression has been performed is expired, a part of thepieces of UDC-compressed data may be discarded, and thus the receptionnode may fail to perform UDC decompression on pieces of UDC-compresseddata after the discarded part of data.

In the following description, the disclosure proposes the (1-1)thembodiment for, when a transmission PDCP layer device discards data towhich UDC compression has been performed, by a PDCP discard timer,preventing data loss and reducing pieces of data in which a checksumfailure occurs, in a reception node.

-   -   Operation of transmission node: in a case where an uplink data        compression process is configured in a transmission PDCP layer        device, if data which has not been transmitted yet and has been        UDC-compressed is discarded by expiration of a PDCP discard        timer, a transmission node may transmit data which has a PDCP        sequence number larger than that of the discarded data and has        been UDC-compressed; discard all the pieces of remaining data        (pieces of data, for example, PDCP PDUs, each of which have a        PDCP sequence number larger than that next to the discarded        data, to which user data compression has been applied, and which        have not been transmitted yet and have been stored); and        transmit, to a lower layer device, an indicator discarding the        pieces of data if the pieces of data have been transferred        already to the lower layer device. The transmission node may        stop data transmission with respect to the transmission PDCP        layer device until a PDCP control PDU indicating that a checksum        failure has occurred is received. This is because an        intermediate piece or a part of the pieces of UDC-compressed        data has been discarded, and thus user data compression is        performed previously, and it is obvious that a checksum failure        relating to pieces of data (e.g., PDCP PDU) each having a PDCP        sequence number larger than that of the discarded piece of data        will occur in a reception PDCP layer device. Therefore, the        transmission node may expect that if the transmission node        transmits data corresponding to a PDCP sequence number next to        the discarded data, the reception PDCP layer device identifies a        checksum failure and transmits a PDCP control PDU to the        transmission node.    -   Therefore, if the transmission PDCP layer device has received a        PDCP control PDU indicating that a checksum failure has        occurred, or before the PDCP control PDU is received, the        transmission PDCP layer device initializes a transmission buffer        for user data compression (if the transmission UDC buffer is        initialized previously, the transmission PDCP layer device does        not initialize the transmission buffer for user data        compression) and is required to apply the user data compression        process again first on pieces of raw data (e.g., PDCP SDU) of        pieces of data, of which a PDCP discard timer has not yet        expired and which have not been transmitted yet, or raw data        (e.g., PDCP SDU) of data (data corresponding to a PDCP sequence        number next to discarded data and thus having been transmitted),        of which a PDCP discard timer has not yet expired and which has        been transmitted lastly. In this case, the transmission PDCP        layer may apply the user data compression process and assign        numbers from a new PDCP sequence number or a first PDCP sequence        number which has not been transmitted yet, in an ascending order        to encode, generate, and prepare data (e.g., PDCP PDU). The        transmission PDCP layer device may restart transmission of the        newly generated and prepared pieces of data (e.g., PDCP PDU)        after the PDCP control PDU indicating that the checksum failure        has occurred is received. That is, the transmission PDCP layer        device may transfer data to a lower layer device.

In another method, when the transmission PDCP layer device may newlyapply user data compression, based on raw data (e.g., PDCP SDU) of apiece of discarded data (e.g., PDCP PDU) and apply integrity protectionor an encoding process to newly generate pieces of data (e.g., PDCPPDU), the transmission PDCP layer device may assign the newly generatedpieces of data (e.g., PDCP PDU) with numbers from a PDCP sequence numberor a COUNT value next to a PDCP sequence number or a COUNT value of data(e.g., PDCP PDU) transferred to the lower layer lastly or transmittedlastly. As described above, if the transmission PDCP layer device mayassign the newly generated pieces of data (e.g., PDCP PDU) with numbersfrom a PDCP sequence number or a COUNT value next to a PDCP sequencenumber or a COUNT value of data (e.g., PDCP PDU) transferred to thelower layer lastly or transmitted lastly, the occurrence of a PDCPsequence number gap is prevented so as to prevent transmission delaywhich is incurred by a PDCP rearrangement timer triggered by thereception PDCP layer device.

In the disclosure, a PDCP SDU may indicate raw data received by thetransmission PDCP layer device from an upper layer device, and a PDCPPDU may indicate data which the transmission PDCP layer device is totransmit to a lower layer device after completing data processing. Thedata processing may include processing such as integrity protection andverification, header compression, user layer data compression, or anencoding process, which are configured in a PDCP layer device. Inaddition, a PDCP PDU generated through data processing of the PDCP SDUmay be separate data different from the PDCP SDU; even if the PDCP PDUis discarded, the PDCP SDU may be stored, and a PDCP SDU may bediscarded only by a PDCP data discard timer.

Therefore, in a case where a user data compression process isconfigured, if a part of pieces of data which has been previouslygenerated and to which user data compression has been applied isdiscarded by a PDCP discard timer, a checksum failure which may occur inpieces of data each having a PDCP sequence number larger than that ofthe discarded part of data may be reduced, and data may be generatedagain from pieces of data which have not been transmitted yet or lastlytransmitted data (data corresponding to a PDCP sequence number next todiscarded data and thus having been transmitted), so as to prevent dataloss.

-   -   If a reception node (base station) identifies a checksum failure        of a reception UDC buffer for data to which uplink data        compression (UDC) is to be released, the reception node        transmits a PDCP control PDU to a terminal to indicate that a        checksum failure has occurred. As the PDCP control PDU, a new        PDCP control PDU may be defined and used, and a new indicator        may be defined and then included in an existing PDCP control        PDU, whereby the existing PDCP control PDU may be modified and        used. In another method, an indicator resetting a UDC buffer        since a checksum failure has occurred may be defined instead of        a PDCP sequence number and may indicate the reset.    -   Operation of reception node: If a checksum failure has occurred,        the reception node may initialize the UDC buffer immediately.        The reception node rearranges newly received pieces of data        according to PDCP sequence numbers, and then identifies a UDC        header of each piece of data in an ascending order of the PDCP        sequence numbers. The reception node has received an indicator        showing that a transmission node UDC buffer has been reset due        to a UDC checksum failure, and thus the reception node discards        pieces of data which do not include an indication initializing        the reception UDC buffer and are indicated such that UDC        compression has been performed. In addition, if all the pieces        of data, among newly received pieces of data, which do not        include, in each UDC header, an indicator showing that the        transmission node UDC buffer has been reset due to a UDC        checksum failure, and are indicated such that UDC compression        has not been performed, have been received without a gap        according to an order based on PDCP sequence numbers, the        reception node may process the pieces of data in an ascending        order of the PDCP sequence numbers and then transfer same to an        upper layer device. The reception node may initialize the        reception UDC buffer from pieces of data which include, in each        UDC header, an indicator resetting the reception UDC buffer and        indicating that the transmission node UDC buffer has been reset        due to a UDC checksum failure, and may restart decompression on        UDC-compressed pieces of data in the ascending order of the PDCP        sequence numbers.

In the following description, the disclosure proposes the (1-2)thembodiment for, when a transmission PDCP layer device discards data towhich UDC compression has been performed, by a PDCP discard timer,preventing data loss and reducing pieces of data in which a checksumfailure occurs, in a reception node.

In order to solve the problem, in the (1-2)th embodiment, if atransmission PDCP layer device in which a UDC compression process isconfigured discards first data to which UDC compression has been appliedand which has not been transmitted yet, by expiration of a PDCP discardtimer, the transmission PDCP layer device may discard the first data anddiscard all the pieces of second data (e.g., PDCP PDUs) each of whichhas a PDCP sequence number larger than that of the discard first dataand has not been transmitted yet, and has been UDC-compressed andstored. This is because one intermediate piece of data among pieces ofdata to which UDC compression has been consecutively applied is lost,and thus a reception PDCP layer device fails on UDC decompression of UDCcompressed pieces of data after the discarded piece of data and thusdiscards all the data.

The transmission PDCP layer device may discard the first data and theninitialize a transmission UDC buffer to be prepared to newly perform aUDC compression process. The initialization of the UDC buffer mayindicate initializing of all the values of the UDC buffer to be 0. Inanother method, if dictionary information (predefined dictionary) ispreviously configured by an RRC message, the dictionary information maybe indicated to be input as the values of the UDC buffer so as toinitialize the values.

The transmission PDCP layer device has not transmitted pieces of rawdata (e.g., PDCP SDU) of the discarded pieces of second data (e.g., PDCPPDU) yet after initializing the transmission UDC buffer. Therefore, thetransmission PDCP layer device may newly apply a UDC compression processon the pieces of raw data (e.g., PDCP SDU, i.e., raw data to which thePDCP layer device has not applied data processing and which has beenreceived from an upper layer) of the pieces of second data by using theinitialized transmission UDC buffer, generate and configure individualUDC headers, and then apply an encoding process or an integrityprotection process to perform data transmission.

The transmission PDCP layer device may indicate a UDC header of firstdata (PDCP PDU) on which the transmission PDCP layer device performsdata processing by applying a UDC compression process for the first timeafter initializing the transmission UDC buffer, by using a one-bitindicator to initialize a reception UDC buffer of the reception PDCPlayer device. This is because the reception PDCP layer device is unableto identify data to which UDC compression is newly performed after theinitialization of the transmission UDC buffer, and thus the transmissionPDCP layer device may use the one-bit indicator of the UDC buffer toallow the reception PDCP layer device to identify the one-bit indicator,initialize a reception UDC buffer, and perform a UDC decompressionprocess on the data first by using the initialized reception UDC buffer.Therefore, if a one-bit indicator of a UDC header of received data(e.g., PDCP PDU) indicates initializing of a reception UDC buffer, thereception PDCP layer device may identify that the transmission UDCbuffer has been initialized already and UDC compression has been newlyapplied to the data. Therefore, the reception PDCP layer device mayinitialize the reception UDC buffer and apply a UDC decompressionprocess the data first by using the initialized reception UDC buffer.

According to the (1-2)th embodiment, in a case where a user datacompression process is configured, if a part of pieces of data whichhave been generated already and to which user data compression has beenapplied is discarded by a PDCP discard timer, pieces of data, each ofwhich has a PDCP sequence number larger than that of the discarded partof data and to which UDC compression has been applied are nottransmitted. Therefore, decompression failure or checksum failure whichmay occurs in a reception PDCP layer device can be reduced, and a wasteof transmission resources can be reduced. In addition, a transmissionPDCP layer device generates data again from pieces of data which havenot been transmitted yet or lastly transmitted data (data correspondingto a PDCP sequence number next to discarded data and thus having beentransmitted), so as to prevent data loss. In addition, a transmissionPDCP layer device may directly initialize a transmission UDC buffer andnewly start UDC compression without having to wait for PDCP control data(PDCP control PDU) indicating initializing of the transmission UDCbuffer, which is transmitted due to the occurrence of a checksum failurefrom a reception PDCP layer device. Therefore, transmission delay can bereduced. In addition, decompression failure or checksum failure does notoccur in a reception PDCP layer device. Therefore, the reception PDCPlayer device is not required to generate and transmit PDCP control data,and may initialize a reception UDC buffer only according to a one-bitindication of a UDC header, indicated by a transmission PDCP layerdevice, and newly start UDC decompression. Therefore, the (1-2)thembodiment may be a method led by a transmission node (terminal) forinitializing a transmission/reception UDC buffer by using a one-bitindicator of a UDC header.

Specific operations of the (1-2)th embodiment are as follows.

-   -   Operation of transmission node: in a case where an uplink data        compression process is configured in a transmission PDCP layer        device, if data which has not been transmitted yet and has been        UDC-compressed is discarded by expiration of a PDCP discard        timer, a transmission node may discard all the pieces of data        (e.g., PDCP PDU), each of which have a PDCP sequence number        larger than that of the discarded data, or which have been        generated as PDCP PDUs, to which user data compression has been        applied, and which have not been transmitted yet and have been        stored. Furthermore, the transmission node may transmit, to a        lower layer device, an indicator discarding the pieces of data        if the pieces of data have been transferred already to the lower        layer device. The transmission PDCP layer device may initialize        (reset) a buffer (UDC buffer) for transmission user data        compression; assign a new PDCP sequence number or a PDCP        sequence number having not been transmitted yet to data from raw        data (e.g., PDCP SDU) of first data having not been transmitted        yet in an ascending order; perform user data compression again;        and perform encoding. When the transmission node generates a UDC        header of first data to which UDC compression has been applied        for the first time after the initialization of the transmission        UDC buffer, the transmission node may define and indicate a new        one-bit indicator (e.g., an element indicated by reference        numeral 9-05 in FIG. 9) to indicate that the buffer for        transmission user data compression has been initialized, or        indicate initializing of a reception UDC buffer of a reception        node. In addition, the reception node having identified the        one-bit indicator of the UDC header may identify that the        reception node is required to initialize a buffer for reception        user data decompression. In another method, the transmission        node may indicate, by using an FR bit, that the buffer for        transmission user data compression has been initialized and a        reception side is also required to initialize a buffer for        reception user data decompression. That is, the terminal may        initialize transmission and reception UDC buffers.    -   In the transmission node, the transmission PDCP layer device may        directly start to transmit the newly generated and prepared        pieces of data sequentially or in an ascending order based on a        PDCP sequence number from data, a UDC header of which indicates        that the buffer for transmission user data compression has been        initialized and the reception node is also required to        initialize the buffer for reception user data decompression.        That is, the transmission PDCP layer device may transfer data to        a lower layer device.

In another method, when the transmission PDCP layer device may newlyapply user data compression, based on raw data (e.g., PDCP SDU) of apiece of discarded data (e.g., PDCP PDU) and apply integrity protectionor an encoding process to newly generate pieces of data (e.g., PDCPPDU), the transmission PDCP layer device may assign the newly generatedpieces of data (e.g., PDCP PDU) with numbers from a PDCP sequence numberor a COUNT value next to a PDCP sequence number or a COUNT value of data(e.g., PDCP PDU) transferred to the lower layer lastly or transmittedlastly. As described above, if the transmission PDCP layer device mayassign the newly generated pieces of data (e.g., PDCP PDU) with numbersfrom a PDCP sequence number or a COUNT value next to a PDCP sequencenumber or a COUNT value of data (e.g., PDCP PDU) transferred to thelower layer lastly or transmitted lastly, the occurrence of a PDCPsequence number gap is prevented so as to prevent transmission delaywhich is incurred by a PDCP rearrangement timer triggered by thereception PDCP layer device.

In the (1-2)th embodiment, the terminal may trigger a process ofinitializing transmission and reception UDC buffers by using a one-bitindicator of a UDC header, by terminal itself before a checksum failure.

Therefore, in a case where a user data compression process isconfigured, if a part of pieces of data which has been previouslygenerated and to which user data compression has been applied isdiscarded by a PDCP discard timer, a checksum failure which may occur inpieces of data each having a PDCP sequence number larger than that ofthe discarded part of data may be reduced, and the transmission node mayregenerate pieces of data having not been transmitted yet, so as toprevent data loss.

-   -   Operation of reception node: if a UDC header of received data        indicates that a buffer for transmission user data compression        has been initialized and the reception side is also required to        initialize a buffer for reception user data decompression, the        reception node may reset a reception node UDC buffer, decode        received pieces of data in an ascending order based on a PDCP        sequence number, perform user data decompression and processing        on the decoded pieces of data, and transfer the pieces of data        to an upper layer device.

In the above description of the disclosure, if a user data compressionprocess is configured, and data to which the user data compressionprocess has been applied is received, the reception PDCP layer devicemay identify a checksum field of a user data compression header of thedata. If a checksum failure occurs, the reception PDCP layer device maytrigger a PDCP control PDU, configure an indicator indicating that thechecksum failure has occurred, and configure and generate the PDCPcontrol PDU to transmit same to the transmission node.

However, the reception PDCP layer device may receive a plurality ofpieces of data, and several checksum failures may occur. If thereception node generates a plurality of PDCP control PDUs at every timewhen a checksum failure occur, and transmits the plurality of PDCPcontrol PDUs to the transmission node, a user data compression buffer ofthe transmission node is unnecessarily initialized several times, and auser data compression process is incurred again.

Therefore, in order to solve the problem, the disclosure proposes aprocess in which a PDCP control PDU is not additionally generated andtransmitted until a predetermined condition is satisfied after areception PDCP layer device transmits a PDCP control PDU due to achecksum failure. The above described predetermined condition is thatthe reception PDCP layer device receives data, among pieces of datareceived after the transmission of the PDCP control PDU, indicating thata transmission user data compression buffer has been initialized and thedata is first data to which user data compression has been appliednewly, through a one-bit indicator of a user data compression header ofthe data. Specifically, a proposed operation of the reception PDCP layerdevice prevents additional generation of a PDCP control PDU due to achecksum failure until the reception PDCP layer device receives dataindicating, through a one-bit indicator of a user data compressionheader of the data, that a transmission user data compression buffer hasbeen initialized and the data is first data to which user datacompression has been applied newly, among pieces of data received afterthe transmission of the PDCP control PDU due to a checksum failure.Therefore, unnecessary transmission of a PDCP control PDU can beprevented.

In another method, a new timer is employed. When the reception PDCPlayer device generates and transmits a PDCP control PDU as describedabove, the reception PDCP layer device may start the timer, and may notgenerate an additional PDCP control PDU due to a checksum failure duringthe operation of the timer. In this case, if the reception PDCP layerdevice receives data indicating, through a one-bit indicator of a userdata compression header, that a transmission user data compressionbuffer has been initialized and the data is first data to which userdata compression has been applied newly, the reception PDCP layer devicemay stop the timer. If data in which the one-bit indicator is configuredis not received until the timer is expired, the reception PDCP layerdevice may trigger and generate a PDCP control PDU indicating a checksumfailure again, after the expiration of the timer and then transmit thePDCP control PDU.

In the above description of the disclosure, if the transmission PDCPlayer device has received a PDCP control PDU (a PDCP control PDUincluding an indicator indicating that a checksum failure has occurred),the transmission PDCP layer device may initialize a transmission userdata compression buffer; newly apply a user data compression process onpieces of data which has not been transmitted yet; use a one-bitindicator of a user data compression header of newly compressed firstdata to indicate that the buffer has been initialized and the data isthe newly compressed first data; and transmit the pieces of data.

If a plurality of PDCP control PDUs (a PDCP control PDU including anindicator indicating that a checksum failure has occurred) are receivedseveral times, the transmission PDCP layer device may initialize thetransmission user data compression buffer several times and newly applya user data compression process on pieces of data having not beentransmitted yet several times, so that unnecessary data processing isincurred and thus the battery of the terminal is wasted and processingload is increased.

Therefore, in order to solve the problem, the disclosure proposes aprocess in which, if a PDCP control PDU (a PDCP control PDU including anindicator indicating that a checksum failure has occurred) is received,a transmission PDCP layer device initializes a transmission user datacompression buffer, newly applies a user data compression process onpieces of data having not been transmitted yet, and ignores anadditionally received PDCP control PDU (a PDCP control PDU including anindicator indicating that a checksum failure has occurred) until apredetermined condition is satisfied. The above described predeterminedcondition is that the transmission PDCP layer device receives a PDCPcontrol PDU, initializes a transmission user data compression buffer,transmits first data to which user data compression has been appliednewly, and identifies a successful transfer (RLC ACK) of the first data,from a lower layer device. Specifically, in a proposed operation of thetransmission PDCP layer device, the transmission PDCP layer devicereceives a PDCP control PDU, initializes a transmission user datacompression buffer, transmits first data to which user data compressionhas been performed newly, and ignores an additionally received PDCPcontrol PDU (a PDCP control PDU including an indicator indicating that achecksum failure has occurred) until a successful transfer (RLC ACK) ofthe first data is identified from a lower layer device. Therefore,unnecessary processing delay due to a plurality of PDCP control PDUs (aPDCP control PDU including an indicator indicating that a checksumfailure has occurred) can be prevented (i.e., buffer initialization anddata discard and then new compression).

FIG. 10 is a diagram illustrating a terminal operation performed when atransmission node PDCP layer device drives a PDCP discard timer and datahaving not been transmitted yet and having been subjected to a usercompression process (e.g., UDC) is discarded due to the expiration ofthe PDCP discard timer in the disclosure according to an embodiment ofthe disclosure.

Referring to FIG. 10, a terminal (or transmission node) may operate aPDCP discard timer for each received data at every time when theterminal receives data from an upper layer device (operation 10-05)(operation 10-10). If a PDCP layer device is configured to performuplink data compression with respect to the data (PDCP SDU), thetransmission node performs uplink data compression on the received data.The transmission node performs uplink data compression (UDC), updates abuffer according to the data compression, and configures a transmissionUDC buffer. If the transmission node performs uplink data compression(UDC) as described above, the transmission node may compress a PDCP SDUreceived from an upper layer to be UDC compression data (UDC block)having a smaller size (operation 10-15). The transmission nodeconfigures a UDC header relating to the compressed UDC compression data.The UDC header may include an indicator indicating whether uplink datacompression has been performed or not (e.g., if a one-bit indicator ofthe UDC header is 0, this implies UDC has been applied, and if theindicator is 1, this implies UDC has been unapplied).

In the above description, if the terminal performs uplink datacompression (UDC) on data (PDCP SDU) received from the upper layer andupdates a UDC buffer, the transmission node may calculate checksum bitsand include same in the UDC buffer in order to allow a reception nodePDCP layer device to check the validity of the updated UDC buffer (thechecksum bits have a predetermined length, and may be configured by 4bits, for example).

The terminal performs integrity protection data to which uplink datadecompression has been applied or not as described above, if theintegrity protection is configured, encodes (ciphering) the data, andthen transfers the data to a lower layer.

If a transmission PDCP layer device discards data which has not beentransmitted yet and has been UDC-compressed, by expiration (operation10-20) of a PDCP discard timer (operation 10-30), the transmission nodemay transmit data corresponding to a PDCP sequence number next to thediscarded data; discard all the pieces of remaining data (pieces ofdata, each of which have a PDCP sequence number larger than that next tothe discarded data, to which user data compression has been applied, andwhich have not been transmitted yet and have been stored); and transmit,to a lower layer device, an indicator discarding the pieces of data ifthe pieces of data have been transferred already to the lower layerdevice. The transmission node may stop data transmission with respect tothe transmission PDCP layer device until a PDCP control PDU indicatingthat a checksum failure has occurred is received. This is because anintermediate piece or a part of the pieces of UDC-compressed data hasbeen discarded, and thus user data compression is performed previously,and it is obvious that a checksum failure relating to pieces of data(e.g., PDCP PDU) each having a PDCP sequence number larger than that ofthe discarded piece of data will occur in a reception PDCP layer device.Therefore, the transmission node may expect that if the transmissionnode transmits data corresponding to a PDCP sequence number next to thediscarded data, the reception PDCP layer device identifies a checksumfailure and transmits a PDCP control PDU to the transmission node.

Therefore, if the transmission PDCP layer device has received a PDCPcontrol PDU indicating that a checksum failure has occurred, or beforethe PDCP control PDU is received, the transmission PDCP layer device mayinitialize a transmission buffer for user data compression (if thetransmission UDC buffer is initialized previously, the transmission PDCPlayer device does not initialize the transmission buffer for user datacompression), perform a user data compression process again first onpieces of data, of which a PDCP discard timer has not yet expired andwhich have not been transmitted yet, or data (data corresponding to aPDCP sequence number next to discarded data and thus having beentransmitted), of which a PDCP discard timer has not yet expired andwhich has been transmitted lastly, assign numbers from a new PDCPsequence number or a first PDCP sequence number which has not beentransmitted yet, in an ascending order to encode, generate, and preparedata (e.g., PDCP PDU). The transmission PDCP layer device may restarttransmission of the newly generated and prepared pieces of data afterthe PDCP control PDU indicating that the checksum failure has occurredis received. That is, data may be transferred to a lower layer device.

If a PDCP discard timer is not expired in the transmission PDCP layerdevice, the transmission node transfers data to the lower layer deviceto transmit the data to a reception node (operation 10-25).

According to the above described embodiment, in the (1-1)th embodiment,when the transmission node discards data having not been transmitted yetand having been UDC-compressed due to the expiration of a PDCP discardtimer, the transmission node may transmit the data without discarding ordiscard the data; transmit first data having a PDCP sequence numberlarger than that of the data and having been UDC-compressed; and discardall the pieces of remaining data (pieces of data, each of which have aPDCP sequence number larger than that of the discarded or transmitteddata, to which user data compression has been applied, and which havenot been transmitted yet and have been stored). In addition, thetransmission node may transmit an indicator discarding the pieces ofdata if same has been transferred already, to the lower layer device.The transmission node may stop data transmission with respect to thetransmission PDCP layer device until a PDCP control PDU indicating thata checksum failure has occurred is received. This is because anintermediate piece or a part of the pieces of UDC-compressed data hasbeen discarded, and thus user data compression is performed previously,and it is obvious that a checksum failure relating to pieces of data(e.g., PDCP PDU) each having a PDCP sequence number larger than that ofthe discarded piece of data will occur in a reception PDCP layer device.Therefore, the transmission node may expect that if the transmissionnode transmits discarded data or first data having a PDCP sequencenumber larger than that of the discarded data and having beenUDC-compressed, the reception PDCP layer device identifies a checksumfailure and transmits a PDCP control PDU to the transmission node.

Therefore, the transmission PDCP layer device may receive a PDCP controlPDU indicating that a checksum failure has occurred, or may initialize atransmission buffer for user data compression before the PDCP controlPDU is received (if a transmission UDC buffer has been initializedalready in the above description, the transmission buffer is notinitialized). In addition, the transmission PDCP layer device mayperform a user data compression process again first on pieces of data,of which a PDCP discard timer has not yet expired and which have notbeen transmitted yet, or data (discarded data or first data having aPDCP sequence number larger than that of the discarded data and havingbeen UDC-compressed), of which a PDCP discard timer has not yet expiredand which has been transmitted lastly, assign numbers from a new PDCPsequence number or a first PDCP sequence number which has not beentransmitted yet, in an ascending order to encode, generate, and preparedata (e.g., PDCP PDU). The transmission PDCP layer device may restarttransmission of the newly generated and prepared pieces of data afterthe PDCP control PDU indicating that the checksum failure has occurredis received. That is, the transmission PDCP layer device may transferdata to the lower layer device.

According to the (1-1)th embodiment, in a case where a user datacompression process is configured, if a part of pieces of data whichhave been generated already and to which user data compression has beenapplied is discarded by a PDCP discard timer, pieces of data, each ofwhich has a PDCP sequence number larger than that of the discarded partof data and to which UDC compression has been applied are nottransmitted. Therefore, decompression failure or checksum failure whichmay occurs in the reception PDCP layer device can be reduced, and awaste of transmission resources can be reduced. In addition, data isgenerated again from pieces of data which have not been transmitted yetor lastly transmitted data (data corresponding to a PDCP sequence numbernext to discarded data and thus having been transmitted), so as toprevent data loss.

In order to solve the problem, in the (1-2)th embodiment, if atransmission PDCP layer device in which a UDC compression process isconfigured discards first data to which UDC compression has been appliedand which has not been transmitted yet, by expiration of a PDCP discardtimer, the transmission PDCP layer device may discard the first data anddiscard all the pieces of second data (e.g., PDCP PDUs) each of whichhas a PDCP sequence number larger than that of the discard first dataand has not been transmitted yet, and has been UDC-compressed andstored. This is because one intermediate piece of data among pieces ofdata to which UDC compression has been consecutively applied is lost,and thus a reception PDCP layer device fails on UDC decompression of UDCcompressed pieces of data after the discard piece of data, and thusdiscards all the failed pieces of data.

The transmission PDCP layer device may discard the first data and theninitialize a transmission UDC buffer to be prepared to newly perform aUDC compression process. The initialization of the UDC buffer mayindicate initializing of all the values of the UDC buffer to be 0. Inanother method, if dictionary information (predefined dictionary) ispreviously configured by an RRC message, the dictionary information maybe indicated to be input as the values of the UDC buffer so as toinitialize the values. The transmission PDCP layer device has nottransmitted pieces of raw data (e.g., PDCP SDU) of the discarded piecesof second data (e.g., PDCP PDU) yet after initializing the transmissionUDC buffer. Therefore, the transmission PDCP layer device may newlyapply a UDC compression process on the pieces of raw data (e.g., PDCPSDU, i.e., raw data to which the PDCP layer device has not applied dataprocessing and which has been received from an upper layer) of thepieces of second data by using the initialized transmission UDC buffer,generate and configure individual UDC headers, and then apply anencoding process or an integrity protection process to perform datatransmission. The transmission PDCP layer device may indicate a UDCheader of first data (PDCP PDU) on which the transmission PDCP layerdevice performs data processing by applying a UDC compression processfor the first time after initializing the transmission UDC buffer, byusing a one-bit indicator to initialize a reception UDC buffer of thereception PDCP layer device. This is because the reception PDCP layerdevice is unable to identify data to which UDC compression is newlyperformed after the initialization of the transmission UDC buffer, andthus the transmission PDCP layer device may use the one-bit indicator ofthe UDC buffer to allow the reception PDCP layer device to identify theone-bit indicator, initialize a reception UDC buffer, and perform a UDCdecompression process on the data first by using the initializedreception UDC buffer. Therefore, if a one-bit indicator of a UDC headerof received data (e.g., PDCP PDU) indicates initializing of a receptionUDC buffer, the reception PDCP layer device may identify that thetransmission UDC buffer has been initialized already and UDC compressionhas been newly applied to the data Therefore, the reception PDCP layerdevice may initialize the reception UDC buffer and apply a UDCdecompression process the data first by using the initialized receptionUDC buffer.

According to the (1-2)th embodiment, in a case where a user datacompression process is configured, if a part of pieces of data whichhave been generated already and to which user data compression has beenapplied is discarded by a PDCP discard timer, pieces of data, each ofwhich has a PDCP sequence number larger than that of the discarded partof data and to which UDC compression has been applied are nottransmitted. Therefore, decompression failure or checksum failure whichmay occurs in a reception PDCP layer device can be reduced, and a wasteof transmission resources can be reduced. In addition, data is generatedagain from pieces of data which have not been transmitted yet or lastlytransmitted data (data corresponding to a PDCP sequence number next todiscarded data and thus having been transmitted), so as to prevent dataloss. In addition, a transmission PDCP layer device may directlyinitialize a transmission UDC buffer and newly start UDC compressionwithout having to wait for PDCP control data (PDCP control PDU)indicating initializing of the transmission UDC buffer, which istransmitted due to the occurrence of a checksum failure from a receptionPDCP layer device. Therefore, transmission delay can be reduced.Decompression failure or checksum failure does not occur in a receptionPDCP layer device. Therefore, the reception PDCP layer device is notrequired to generate and transmit PDCP control data, and may initializea reception UDC buffer only according to a one-bit indication of a UDCheader, indicated by a transmission PDCP layer device, and newly startUDC decompression. Therefore, the (1-2)th embodiment may be a method ledby a terminal for initializing a transmission/reception UDC buffer byusing a one-bit indicator of a UDC header.

In the disclosure, a PDCP SDU may indicate raw data received by thetransmission PDCP layer device from an upper layer device, and a PDCPPDU may indicate data which the transmission PDCP layer device is totransmit to a lower layer device after completing data processing. Thedata processing may include processing such as integrity protection andverification, header compression, user layer data compression, or anencoding process, which are configured in a PDCP layer device. Inaddition, a PDCP PDU generated through data processing of the PDCP SDUmay be separate data different from the PDCP SDU; even if the PDCP PDUis discarded, the PDCP SDU may be stored, and a PDCP SDU may bediscarded only by a PDCP data discard timer.

In the follow description in the disclosure, a method for effectivelyperforming a user data compression method (UDC) proposed in thedisclosure in a case where a service data adaptation protocol (SDAP)layer device is configured or an SDAP header is configured is proposed.

In the disclosure, the (2-1)th embodiment in which a user datacompression method is efficiently performed in a case where an SDAPlayer device or an SDAP header is configured by an RRC message isproposed as follows. In the (2-1)th embodiment, an SDAP header iscompressed by using a user data compression method, and a UDC header isencoded. According to the (2-1)th embodiment, through the abovedescribed features, the same process may be performed on upper layerdata regardless of whether an SDAP header exists or not, so as toimprove convenience of implementation, and a UDC header may be encodedto reinforce security.

FIG. 11 is a diagram illustrating the (2-1)th embodiment in which a userdata compression method is efficiently performed in a case where an SDAPlayer device or an SDAP header is configured through an RRC messageaccording to an embodiment of the disclosure.

Referring to FIG. 11, in a case where an SDAP layer device or an SDAPheader is configured to be used by an RRC message, for example, inoperation 5-10, 5-40, or 5-75 in FIG. 5, and user data compression (UDC)is configured, if the SDAP layer device receives data from an upperlayer, the SDAP layer device may generate and configure an SDAP headeras an element indicated by reference numeral 11-05 and transfer the dataand the SDAP header to a PDCP layer device. The PDCP layer device 11-01may perform user data compression on a PDCP SDU (SDAP header and IPpacket, as indicated by reference numeral 11-06) received from the upperSDAP layer device (operation 11-07). The PDCP layer device may calculatea checksum field and configure whether UDC has been applied, to generatea UDC header and attach same (as indicated by reference numeral 11-10).The PDCP layer device may encode the UDC header and a compressed UDCblock, generate and configure a PDCP header 11-20, bond the PDCP headerto the encoded UDC header and UDC block, and then transfer the headersand the UDC block to a lower layer to proceed data processing in an RLClayer device and an MAC layer device.

In the process described with reference to FIG. 11, an SDAP header iscompressed by using a user data compression method, a UDC header and anSDAP header 11-15 are encoded. Through the above described features, thesame process may be performed on upper layer data regardless of whetheran SDAP header exists or not, so as to improve convenience ofimplementation, and a UDC header may be encoded to reinforce security.

In the disclosure, the (2-2)th embodiment in which a user datacompression method is efficiently performed in a case where an SDAPlayer device or an SDAP header is configured by an RRC message isproposed as follows. In the (2-2)th embodiment, a user data compressionmethod is not applied to an SDAP header, the SDAP header is not encoded,and a UDC header is encoded. According to the (2-2)th embodiment,through the above described features, QoS information of an SDAP headercan be utilized without a decoding process of information of the SDAPheader by a transmission node or a reception node. For example, a basestation may use the QoS information for scheduling. Furthermore, in acase of implementation of a terminal, there is no need to generate anSDAP header at every time when upper layer data is received, a hardwareaccelerator may perform a UDC process, perform encoding, and attach anSDAP header later, so as to facilitate the implementation of a terminal.In addition, a UDC header may be encoded to reinforce security.

FIG. 12 is a diagram illustrating the (2-2)th embodiment in which a userdata compression method is efficiently performed in a case where an SDAPlayer device or an SDAP header is configured through an RRC message inthe disclosure according to an embodiment of the disclosure.

Referring to FIG. 12, in a case where an SDAP layer device or an SDAPheader is configured to be used by an RRC message, for example, inoperation 5-10, 5-40, or 5-75 in FIG. 5, and user data compression (UDC)is configured, if the SDAP layer device receives data from an upperlayer, the SDAP layer device may generate and configure an SDAP headeras an element indicated by reference numeral 12-05 and transfer the dataand the SDAP header to a PDCP layer device. The PDCP layer device 12-01may perform a user data compression process on a PDCP SDU (SDAP headerand remaining data part, excluding an SDAP header from IP packet)received from the upper SDAP layer device (operation 12-07). The PDCPlayer device may calculate a checksum field and configure whether UDChas been applied, to generate a UDC header and attach same to the frontof the SDAP header (as indicated by reference numeral 12-10). Ifintegrity protection is configured, the PDCP layer device may applyintegrity protection to the UDC header and compressed UDC block beforean encoding process, and then encode the compressed UDC block andseparately encode the UDC header to encode the UDC header and the UDCblock (operations 12-15 and 12-20). In order to perform the encodingprocess only one time, the PDCP layer device may separate the SDAPheader in the process of the above described operations, encode the UDCheader and the UDC block in one stage, insert the unencoded SDAP headerbetween the UDC header and the UDC block to configure data, generate andconfigure a PDCP header 12-20 to bond the same to the data, thentransfer the data and the PDCP header and UDC header 12-25 to a lowerlayer to proceed data processing in an RLC layer device and an MAC layerdevice.

In the disclosure, the (2-3)th embodiment in which a user datacompression method is efficiently performed in a case where an SDAPlayer device or an SDAP header is configured by an RRC message isproposed as follows. In the (2-3) th embodiment, a user data compressionmethod is not applied to an SDAP header, the SDAP header is not encoded,and a UDC header is also not encoded. Through the above describedfeatures, QoS information of an SDAP header can be utilized without adecoding process of information of the SDAP header by a transmissionnode or a reception node. For example, a base station may use the QoSinformation for scheduling. Furthermore, in a case of implementation ofa terminal, there is no need to generate an SDAP header at every timewhen upper layer data is received, a hardware accelerator may perform aUDC process, perform encoding, and attach an SDAP header later, so as tofacilitate the implementation of a terminal. Furthermore, a UDC headeris not encoded either, and thus a user data compression process and anencoding process can be continuously performed on data received from anupper layer by an SDAP layer device, by means of a hardware accelerator,and after data processing of an PDCP layer device is completed, an SDAPheader, a UDC header, and a PDCP header, which are generated, can beattached to the very front of data for which the data processing iscompleted, and then the headers and the data can be transferred to alower layer. Therefore, implementation of a terminal is simple. Inaddition, if a UDC header is not encoded in the process, a receptionnode may firstly read and calculate a checksum field of a UDC headerbefore performing decoding (deciphering), so as to identify the validityof a UDC buffer contents. Therefore, if a checksum failure occurs, thereception node may not perform a decoding process, discard correspondingdata immediately, and perform a checksum failure processing process, soas to reduce processing burden.

FIG. 13 is a diagram illustrating the (2-3)th embodiment in which a userdata compression method is efficiently performed in a case where an SDAPlayer device or an SDAP header is configured through an RRC message inthe disclosure according to an embodiment of the disclosure.

Referring to FIG. 13, in a case where an SDAP layer device function oran SDAP header is configured to be used by an RRC message, for example,in operation 5-10, 5-40, or 5-75 in FIG. 5, and user data compression(UDC) is configured, if the SDAP layer device receives data from anupper layer, the SDAP layer device may generate and configure an SDAPheader as an element indicated by reference numeral 13-05 and transferthe data and the SDAP header to a PDCP layer device. The PDCP layerdevice 13-01 may perform user data compression on a PDCP SDU (SDAPheader and remaining data part, excluding an SDAP header from IP packet)received from the upper SDAP layer device (operation 13-07). Ifintegrity protection is configured, the PDCP layer device may applyintegrity protection to a UDC block having been compressed through theuser data compression, a UDC header, an SDAP header, and a PDCP headerbefore an encoding process. The PDCP layer device may encode only theUDC block having been compressed through the user data compression,except the UDC header and the SDAP header (operation 13-10). The PDCPlayer device may calculate a checksum field and configure whether UDChas been applied, to generate a UDC header and attach same (operations13-15 and 13-20). The PDCP layer device may generate, configure, andbond a PDCP header and then transfer the PDCP header to a lower layer toproceed data processing in an RLC layer device and an MAC layer device.As proposed in the above description, if a user data compression is notapplied to an SDAP header and encoding is not applied to a UDC header, auser data compression process and an encoding or decoding process issimplified and a complex process is omitted in implementation of aterminal and a base station, so as to simplify a processing process ofthe implementation and reduce processing burden.

In the disclosure, the (2-4)th embodiment in which a user datacompression method is efficiently performed in a case where an SDAPlayer device or an SDAP header is configured by an RRC message isproposed as follows. In the (2-4) th embodiment, a user data compressionmethod is not applied to an SDAP header, an SDAP header is not encoded,and a UDC header is encoded. Furthermore, the UDC header is attached tothe rear of the SDAP header, or the UDC header is attached to the veryfront of a compressed UDC block and the SDAP header is attached to thefront of the UDC header. Through the above described features, QoSinformation of an SDAP header can be utilized without a decoding processof information of the SDAP header by a transmission node or a receptionnode. For example, a base station may use the QoS information forscheduling. Furthermore, in a case of implementation of a terminal,there is no need to generate an SDAP header at every time when upperlayer data is received, a hardware accelerator may perform a UDCprocess, directly generate and attach a UDC header, perform encoding,and attach an SDAP header later, so as to facilitate the implementationof a terminal. In addition, a UDC header may be encoded to reinforcesecurity. In addition, in the embodiment, the position of the SDAPheader and the position of the UDC header are changed, so that when auser data compression process is performed, unnecessary processes ofperforming processing except the SDAP header, or detaching the SDAPheader, performing processing, and then attaching the SDAP back can bereduced, and an one integrated process can be performed on a UDC headerand a UDC data block.

FIG. 14 is a diagram illustrating the (2-4)th embodiment in which a userdata compression method is efficiently performed in a case where an SDAPlayer device or an SDAP header is configured through an RRC message inthe disclosure according to an embodiment of the disclosure.

Referring to FIG. 14, in a case where an SDAP layer device or an SDAPheader is configured to be used by an RRC message, for example, inoperation 5-10, 5-40, or 5-75 in FIG. 5, and user data compression (UDC)is configured, if the SDAP layer device receives data from an upperlayer, the SDAP layer device may generate and configure an SDAP headeras an element indicated by reference numeral 14-05 and transfer the dataand the SDAP header to a PDCP layer device. The PDCP layer device 14-01may perform a user data compression process on a PDCP SDU (SDAP headerand remaining data part, excluding an SDAP header from IP packet)received from the upper SDAP layer device (operation 14-07). The PDCPlayer device may calculate a checksum field and configure whether UDChas been applied, to generate a UDC header and attach same to the veryfront of a compressed UDC data block (to the rear of the SDAP header)(as indicated by reference numeral 14-15). If integrity protection isconfigured, PDCP layer device may apply integrity protection to the SDAPheader, the UDC header, the compressed UDC block, and a PDCP headerbefore an encoding process, and then encode the UDC header and thecompressed UDC block (operation 14-10). The PDCP layer device mayconfigure data, generate and configure a PDCP header 14-20, bond theSDAP header first, then bond the PDCP header, and then transfer the dataand the headers to a lower layer to proceed data processing in an RLClayer device and an MAC layer device.

In the disclosure, the (2-5)th embodiment in which a user datacompression method is efficiently performed in a case where an SDAPlayer device or an SDAP header is configured by an RRC message isproposed as follows. In the (2-5) th embodiment, a user data compressionmethod is not applied to an SDAP header, an SDAP header is not encoded,and a UDC header is not encoded either. Furthermore, the UDC header isattached to the rear of the SDAP header, or the UDC header is attachedto the very front of a compressed UDC block and the SDAP header isattached to the front of the UDC header. Through the above describedfeatures, QoS information of an SDAP header can be utilized without adecoding process of information of the SDAP header by a transmissionnode or a reception node. For example, a base station may use the QoSinformation for scheduling. Furthermore, in a case of implementation ofa terminal, there is no need to attach an SDAP header at every time whenupper layer data is received, a hardware accelerator may perform a UDCprocess, perform encoding, directly generate and attach a UDC header,and attach an SDAP header later, so as to facilitate the implementationof a terminal. In addition, in implementation, a user data compressionprocess and an encoding process may be performed on pieces of datareceived from an upper layer by an SDAP layer device, by means of ahardware accelerator, and an SDAP header, a UDC header, and a PDCPheader may be generated in parallel, so that the headers are bondedtogether to the front of data output as a result of the hardwareaccelerator and then transferred to a lower layer to reduce thecomplexity of terminal implementation. In addition, in the embodiment,the position of the SDAP header and the position of the UDC header arechanged, so that when a user data compression process is performed,unnecessary processes of performing processing except the SDAP header,or detaching the SDAP header, performing processing, and then attachingthe SDAP header back can be reduced, and an one integrated process canbe performed on a UDC header and a UDC data block. In addition, the UDCheader is not encoded. Therefore, the reception node can previouslyidentify whether a checksum failure occurs, before performing decoding.If a checksum failure occurs, the reception node can discard data beforedecoding, and directly perform a checksum failure processing process.

FIG. 15 is a diagram illustrating the (2-5)th embodiment in which a userdata compression method is efficiently performed in a case where an SDAPlayer device or an SDAP header is configured through an RRC message inthe disclosure according to an embodiment of the disclosure.

Referring to FIG. 15, in a case where an SDAP layer device or an SDAPheader is configured to be used by an RRC message, for example, inoperation 5-10, 5-40, or 5-75 in FIG. 5, and user data compression(uplink data compression, UDC) is configured, if the SDAP layer devicereceives data from an upper layer, the SDAP layer device may generateand configure an SDAP header as an element indicated by referencenumeral 15-05 and transfer the data and the SDAP header to a PDCP layerdevice. The PDCP layer device 15-01 may perform a user data compressionprocess on a PDCP SDU (SDAP header and remaining data part, excluding anSDAP header from IP packet) received from the upper SDAP layer device(operation 15-07). The PDCP layer device may calculate a checksum fieldand configure whether UDC has been applied, to generate a UDC header andattach same to the very front of a compressed UDC data block (to therear of the SDAP header) (as indicated by reference numeral 15-15). Ifintegrity protection is configured, the PDCP layer device may applyintegrity protection to the SDAP header, the UDC header, the compressedUDC block, and a PDCP header before an encoding process, and then encodeonly the compressed UDC block except the SDAP header and the UDC header(operation 15-10). The PDCP layer device may configure data, generateand configure a PDCP header 15-20, bond the SDAP header first, then bondthe PDCP header, and then transfer the data and the headers to a lowerlayer to proceed data processing in an RLC layer device and an MAC layerdevice.

In the disclosure, the (2-6)th embodiment in which a user datacompression method is efficiently performed in a case where an SDAPlayer device or an SDAP header is configured by an RRC message isproposed as follows. In the (2-6)th embodiment, an SDAP header iscompressed by using a user data compression method, and a UDC header isnot encoded. According to the (2-6)th embodiment, through the abovedescribed features, the same process may be performed on upper layerdata regardless of whether an SDAP header exists or not, so as toimprove convenience of implementation. In addition, the UDC header isnot encoded. Therefore, the reception node can previously identifywhether a checksum failure occurs, before performing decoding. If achecksum failure occurs, the reception node can discard data beforedecoding, and directly perform a checksum failure processing process.

FIG. 16 is a diagram illustrating the (2-6)th embodiment in which a userdata compression method is efficiently performed in a case where an SDAPlayer device or an SDAP header is configured through an RRC message inthe disclosure according to an embodiment of the disclosure.

Referring to FIG. 16, in a case where an SDAP layer device or an SDAPheader is configured to be used by an RRC message, for example, inoperation 5-10, 5-40, or 5-75 in FIG. 5, and user data compression (UDC)is configured, if the SDAP layer device receives data from an upperlayer, the SDAP layer device may generate and configure an SDAP headeras an element indicated by reference numeral 16-05 and transfer the dataand the SDAP header to a PDCP layer device. The PDCP layer device 16-01may perform user data compression on a PDCP SDU (SDAP header and IPpacket, as indicated by reference numeral 16-06) received from the upperSDAP layer device (operation 16-07). The PDCP layer device may calculatea checksum field and configure whether UDC has been applied, to generatea UDC header and attach same (as indicated by reference numeral 16-10).The PDCP layer device may encode a compressed UDC block except for theUDC header (as indicated by reference numeral 16-15), generate andconfigure a PDCP header 16-20, bond the PDCP header to the UDC header,and then transfer the encoded UDC block and the headers to a lower layerto proceed data processing in an RLC layer device and an MAC layerdevice.

FIG. 17 is a diagram illustrating a terminal operation according to anembodiment of the disclosure.

Referring FIG. 17, a terminal may be configured to apply a user datacompression function by an RRC message, for example, in operation 5-10,5-40, or 5-75 in FIG. 5 (operation 17-05). In addition, if an SDAP layerdevice or an SDAP header is configured to be used in the RRC message(operation 17-10), the (2-1)th embodiment, the (2-2)th embodiment, the(2-3)th embodiment, the (2-4)th embodiment, the (2-5)th embodiment, orthe (2-6)th embodiment in which a user data compression method isefficiently performed when an SDAP layer device or an SDAP header isconfigured in the disclosure may be performed (operation 17-15).However, if an SDAP layer device or an SDAP header is configured not tobe used in the RRC message (operation 17-10), a process, excluding dataprocessing on an SDAP header, from the (2-1)th embodiment, the (2-2)thembodiment, the (2-3)th embodiment, the (2-4)th embodiment, the (2-5)thembodiment, or the (2-6)th embodiment in which a user data compressionmethod is efficiently performed when an SDAP layer device or the SDAPheader is configured in the disclosure may be performed without change(operation 17-20).

In the above disclosure, various cases which may occur due to generationof an SDAP header, an encoding process (ciphering), and an uplink datacompression process (UDC) and the implementation methods accordingthereto are described and proposed.

In the above description, whether an SDAP header is used for each bearermay be configured by a base station through an RRC message as describedwith reference to FIG. 5, and whether UDC is applied for each bearer maybe also configured by a base station through an RRC message as describedabove.

In the following description, the disclosure proposes preventing ofsimultaneous use of an SDAP header and UDC with respect to one bearerwhen a base station configures whether an SDAP header is used for eachbearer and whether UDC is applied for each bearer, through an RRCmessage (The SDAP header cannot be configured for a DRB configured withUDC or Both SDAP header and UDC cannot be configured for a DRB or EitherSDAP header or UDC can be configured for a DRB, not both). That is, abase station may be prohibited from configuring use of an SDAP headerand application of UDC together for one bearer through an RRC message.

As described above, when a UDC process is performed for a bearer forwhich UDC is configured, an SDAP header is generated and unencoded, andthus the UDC process is complex and implementation complexity increases.The UDC is applied to uplink data, and configuring of an SDAP header foruplink data corresponds to configuring of remapping between a bearer anda flow. However, the configuring of an SDAP header for uplink data maybe not suitable for the case where UDC is used. This is because a UDCprocess requires synchronization of a transmission node and a receptionnode for data compression, and thus it is very inefficient to performremapping between a bearer and flows on a bearer to which UDC has beenapplied. Therefore, if use of an SDAP header and configuration of UDCare not configured together for one bearer in order to solve thecomplexity problem, the complex problems described above may not occur.Therefore, the disclosure proposes, as another embodiment, that a basestation does not allow use of an SDAP header and configuration of UDC tobe configured together for one bearer for a terminal

When the base station does not configure use of an SDAP header andconfiguration of UDC together for one bearer for the terminal, a UDCheader may be encoded to reinforce security. That is, if upper layerdata is received, data compression may be performed through a UDCprocess and a UDC header may generated, then the UDC header and acompressed UDC data block may be encoded, a PDCP header may begenerated, and connected and bonded to the front of the encoded UDCheader and UDC data block, and they may be transferred to a lower layer.

In another method, when the base station does not configure use of anSDAP header and configuration of UDC together for one bearer for theterminal, a checksum field of a UDC header may be quickly identified toquickly determine whether to discard UDC data, so that the number oftimes of decoding processes can be reduced. That is, a UDC header maynot be encoded. That is, if upper layer data is received, datacompression may be performed through a UDC process, a compressed datablock may be encoded, a UDC header and a PDCP header may be generated,and connected and bonded to the front of the encoded UDC data block, andthey may be transferred to a lower layer. Therefore, a reception PDCPlayer device may identify a UDC header before decoding; identify thevalidity of UDC through a checksum field; and if it is not valid, doesnot perform decoding and immediately discard the received data. Onlydata, the validity of which has been identified through the checksumfield, may be decoded and subjected to a user data decompressionprocess.

In addition, similarly, an integrity verification protection process mayalso occur a complex implementation problem when the process isconfigured for one bearer together with use of an SDAP header orapplication of UDC. Therefore, use of an SDAP header and integrityverification protection may be not allowed to be configured together forone bearer. In addition, integrity verification and application of UDCmay be not allowed to be configured together for one bearer.

FIG. 18 illustrates a structure of a terminal to which an embodiment maybe applied according to an embodiment of the disclosure.

Referring to FIG. 18, the terminal includes a radio frequency (RF)processor 18-10, a baseband processor 18-20, a storage unit 18-30, and acontroller 18-40.

The RF processor 18-10 performs a function, such as signal band change,amplification, etc., for transmitting or receiving a signal through awireless channel That is, the RF processor 18-10 may upconvert abaseband signal provided from the baseband processor 18-20, into an RFband signal, and then transmit the RF band signal through an antenna,and may downconvert an RF band signal received through the antenna, intoa baseband signal. For example, the RF processor 18-10 may include atransmission filter, a reception filter, an amplifier, a mixer, anoscillator, a digital-to-analog converter (DAC), an analog-to-digitalconverter (ADC), and the like. In FIG. 18, only one antenna isillustrated, but the terminal may include a plurality of antennas. Inaddition, the RF processor 18-10 may include a plurality of RF chains.Furthermore, the RF processor 18-10 may perform beamforming. To performthe beamforming, the RF processor 18-10 may adjust the phase and size ofeach of signals transmitted or received through a plurality of antennasor antenna elements. In addition, the RF process may perform MIMO, andmay receive several layers when a MIMO operation is performed. The RFprocessor 18-10 may properly configure a plurality of antennas orantenna elements according to a control of the controller to performreception beam sweeping or adjust the direction and the beam width of areception beam to be in conjunction with a transmission beam.

The baseband processor 18-20 performs a function of conversion between abaseband signal and a bit stream according to a physical layer protocolof a system. For example, when data is transmitted, the basebandprocessor 18-20 generates complex symbols by encoding and modulating atransmission bit stream. In addition, when data is received, thebaseband processor 18-20 reconstructs a reception bit stream bydemodulating and decoding a baseband signal provided from the RFprocessor 18-10. For example, in a case where an orthogonal frequencydivision multiplexing (OFDM) scheme is applied, when data istransmitted, the baseband processor 18-20 generates complex symbols byencoding and modulating a transmission bit stream, maps the complexsymbols to subcarriers, and then configures OFDM symbols through inversefast Fourier transform (IFFT) calculation and cyclic prefix (CP)insertion. In addition, when data is received, the baseband processor18-20 divides a baseband signal provided from the RF processor 18-10, bythe units of OFDM symbols, reconstructs signals mapped to subcarriers,through fast Fourier transform (FFT) calculation, and then reconstructsa reception bit stream through demodulation and decoding.

The baseband processor 18-20 and the RF processor 18-10 transmit andreceive a signal as described above. Accordingly, the baseband processor18-20 and the RF processor 18-10 may be called a transmitter, areceiver, a transceiver, or a communication unit. Furthermore, at leastone of the baseband processor 18-20 and the RF processor 18-10 mayinclude a plurality of communication modules to support a plurality ofdifferent wireless access technologies. In addition, at least one of thebaseband processor 18-20 and the RF processor 18-10 may includedifferent communication modules to process signals in differentfrequency bands. For example, different wireless access technologies mayinclude LTE network, NR network, etc. In addition, different frequencybands may include a super high frequency (SHF) (e.g., 2.5 GHz and 5 GHz)band, a millimeter (mm) wave (e.g., 60 GHz) band, etc.

The storage unit 18-30 stores data such as a basic program, anapplication program, and configuration information for an operation ofthe terminal. The storage unit 18-30 provides stored data in response toa request of the controller 18-40.

The controller 18-40 controls overall operations of the terminal. Forexample, the controller 18-40 transmits or receives a signal through thebaseband processor 18-20 and the RF processor 18-10. In addition, thecontroller 18-40 records and reads data in and from the storage unit18-40. To this end, the controller 18-40 may include at least oneprocessor. For example, the controller 18-40 may include a communicationprocessor (CP) performing a control for communication, and anapplication processor (AP) controlling a higher layer, such as anapplication program. The controller 18-40 may further include amulti-connection processor 18-42 configured to support multi-connection.

FIG. 19 illustrates a block configuration of a TRP in a wirelesscommunication system to which an embodiment may be applied according toan embodiment of the disclosure.

Referring to FIG. 19, the base station includes a RF processor 19-10, abaseband processor 19-20, a backhaul communication unit 19-30, a storageunit 19-40, and a controller 19-50.

The RF processor 19-10 performs a function, such as signal band change,amplification, etc., for transmitting or receiving a signal through awireless channel That is, the RF processor 19-10 may upconvert abaseband signal provided from the baseband processor 19-20, into an RFband signal, and then transmit the RF band signal through an antenna,and may downconvert an RF band signal received through the antenna, intoa baseband signal. For example, the RF processor 19-10 may include atransmission filter, a reception filter, an amplifier, a mixer, anoscillator, a DAC, an ADC, and the like. In FIG. 19, only one antenna isillustrated, but the first access node may include a plurality ofantennas. In addition, the RF processor 19-10 may include a plurality ofRF chains. Furthermore, the RF processor 19-10 may perform beamforming.To perform the beamforming, the RF processor 19-10 may adjust the phaseand size of each of signals transmitted or received through a pluralityof antennas or antenna elements. The RF processor may perform a downlinkMIMO operation by transmitting at least one layer.

The baseband processor 19-20 performs a function of conversion between abaseband signal and a bit stream according to a physical layer protocolof a first wireless access technology. For example, when data istransmitted, the baseband processor 19-20 generates complex symbols byencoding and modulating a transmission bit stream. In addition, whendata is received, the baseband processor 19-20 reconstructs a receptionbit stream by demodulating and decoding a baseband signal provided fromthe RF processor 19-10. For example, in a case where an OFDM scheme isapplied, when data is transmitted, the baseband processor 19-20generates complex symbols by encoding and modulating a transmission bitstream, maps the complex symbols to subcarriers, and then configuresOFDM symbols through IFFT calculation and CP insertion. In addition,when data is received, the baseband processor 19-20 divides a basebandsignal provided from the RF processor 19-10, by the units of OFDMsymbols, reconstructs signals mapped to subcarriers, through FFTcalculation, and then reconstructs a reception bit stream throughdemodulation and decoding. The baseband processor 19-20 and the RFprocessor 19-10 transmit and receive a signal as described above.Accordingly, the baseband processor 19-20 and the RF processor 19-10 maybe called a transmitter, a receiver, a transceiver, a communicationunit, or a wireless communication unit.

The communication unit 19-30 provides an interface for performingcommunication with other nodes within a network.

The storage unit 19-40 stores data such as a basic program, anapplication program, and configuration information for an operation ofthe main base station. Particularly, the storage unit 19-40 may storeinformation relating to a bearer assigned to a connected terminal, ameasurement result reported from a connected terminal, etc. In addition,the storage unit 19-40 may store information serving as a determinationcriterion of whether to provide or stop providing multi-connection to aterminal. The storage unit 19-40 provides stored data in response to arequest of the controller 19-50.

The controller 19-50 controls overall operations of the main basestation. For example, the controller 19-50 transmits or receives asignal through the baseband processor 19-20 and the RF processor 19-10,or through the backhaul communication unit 19-30. In addition, thecontroller 19-50 records and reads data in and from the storage unit19-40. To this end, the controller 19-50 may include at least oneprocessor. The controller 19-50 may further include a multi-connectionprocessor 19-52 configured to support multi-connection.

While the disclosure has been shown and described with reference tovarious embodiments thereof, it will be understood by those skilled inthe art that various changes in form and details may be made thereinwithout departing from the spirit and scope of the disclosure as definedby the appended claims and their equivalents.

What is claimed is:
 1. A method performed by a transmitting device in awireless communication system, the method comprising: identifying anexpiry of a packet data convergence protocol (PDCP) discard timer for afirst PDCP protocol data unit (PDU) which is not transmitted to areceiving device; discarding all PDCP PDUs which were generated afterthe first PDCP PDU; performing a compression for PDCP service data units(SDUs) corresponding to the discarded PDCP PDUs, starting from a PDCPSDU corresponding to a second PDCP PDU which is subsequent to the firstPDCP PDU; and transmitting, to the receiving device, PDCP PDUs generatedbased on the compression.
 2. The method of claim 1, wherein thediscarding further comprises resetting a user data compression (UDC)buffer.
 3. The method of claim 2, wherein a UDC header of a third PDCPPDU which is a first one among the PDCP PDUs generated based on thecompression includes information indicating that the UDC buffer isreset.
 4. The method of claim 3, wherein the information indicating thatthe UDC buffer is reset includes 1 bit.
 5. The method of claim 1,wherein the transmitting device is a terminal and the receiving deviceis a base station.
 6. A transmitting device in a wireless communicationsystem, the transmitting device comprising: a transceiver configured totransmit or receive a signal; and a controller configured to: identifyan expiry of a packet data convergence protocol (PDCP) discard timer fora first PDCP protocol data unit (PDU) which is not transmitted to areceiving device, discard all PDCP PDUs which were generated after thefirst PDCP PDU, perform a compression for PDCP service data units (SDUs)corresponding to the discarded PDCP PDUs, starting from a PDCP SDUcorresponding to a second PDCP PDU which is subsequent to the first PDCPPDU, and transmit, to the receiving device, PDCP PDUs generated based onthe compression.
 7. The transmitting device of claim 6, wherein thecontroller is further configured to reset a user data compression (UDC)buffer.
 8. The transmitting device of claim 7, wherein a UDC header of athird PDCP PDU which is a first one among the PDCP PDUs generated basedon the compression includes information indicating that the UDC bufferis reset.
 9. The transmitting device of claim 8, wherein the informationindicating that the UDC buffer is reset includes 1 bit.
 10. Thetransmitting device of claim 6, wherein the transmitting device is aterminal and the receiving device is a base station.
 11. A methodperformed by a system including a transmitting device and a receivingdevice, the method comprising: identifying, by the transmitting device,an expiry of a packet data convergence protocol (PDCP) discard timer fora first PDCP protocol data unit (PDU) which is not transmitted to areceiving device; discarding, by the transmitting device, all PDCP PDUswhich were generated after the first PDCP PDU; performing, by thetransmitting device, a compression for PDCP service data units (SDUs)corresponding to the discarded PDCP PDUs, starting from a PDCP SDUcorresponding to a second PDCP PDU which is subsequent to the first PDCPPDU; and transmitting, by the transmitting device to the receivingdevice, PDCP PDUs generated based on the compression.
 12. The method ofclaim 11, wherein the discarding further comprises resetting a user datacompression (UDC) buffer by the transmitting device.
 13. The method ofclaim 12, wherein a UDC header of a third PDCP PDU which is a first oneamong the PDCP PDUs generated based on the compression includesinformation indicating that the UDC buffer is reset.
 14. The method ofclaim 13, wherein the information indicating that the UDC buffer isreset includes 1 bit.
 15. The method of claim 11, wherein thetransmitting device is a terminal and the receiving device is a basestation.
 16. A system comprising: a transmitting device; and a receivingdevice, wherein the transmitting device is configured to: identify anexpiry of a packet data convergence protocol (PDCP) discard timer for afirst PDCP protocol data unit (PDU) which is not transmitted to areceiving device, discard all PDCP PDUs which were generated after thefirst PDCP PDU, perform a compression for PDCP service data units (SDUs)corresponding to the discarded PDCP PDUs, starting from a PDCP SDUcorresponding to a second PDCP PDU which is subsequent to the first PDCPPDU, and transmit, to the receiving device, PDCP PDUs generated based onthe compression.
 17. The system of claim 16, wherein the transmittingdevice is further configured to reset a user data compression (UDC)buffer by the transmitting device.
 18. The system of claim 17, wherein aUDC header of a third PDCP PDU which is a first one among the PDCP PDUsgenerated based on the compression includes information indicating thatthe UDC buffer is reset.
 19. The system of claim 18, wherein theinformation indicating that the UDC buffer is reset includes 1 bit. 20.The system of claim 16, wherein the transmitting device is a terminaland the receiving device is a base station.